diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7476c20776..ae5f499fa2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,13 +15,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.7', '3.8', '3.9', '3.10', '3.11']
+        python: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
         image:
           - ubuntu-latest
         include:
-          - python: '3.11'
+          - python: '3.12'
             image: macos-latest
-          - python: '3.11'
+          - python: '3.12'
             image: windows-latest
     runs-on: '${{ matrix.image }}'
     steps:
@@ -84,7 +84,7 @@ jobs:
     strategy:
       matrix:
         python:
-          - '3.11'
+          - '3.12'
     runs-on: ubuntu-latest
     steps:
       - name: Check out code
@@ -112,6 +112,7 @@ jobs:
       matrix:
         python:
           - '3.11'
+          - '3.12'
     runs-on: ubuntu-latest
     steps:
       - name: Check out code
diff --git a/CHANGES.txt b/CHANGES.txt
index 12e58f07d3..63870f5cca 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -4,11 +4,16 @@ New in master
 Features
 --------
 
+* Implement a new plugin manager from scratch to replace Yapsy,
+  which does not work on Python 3.12 due to Python 3.12 carelessly
+  removing parts of the standard library (Issue #3719)
 * Support for Discourse as comment system (Issue #3689)
 
 Bugfixes
 --------
 
+* Fix loading of templates from plugins with ``__init__.py`` files
+  (Issue #3725)
 * Fix margins of paragraphs at the end of sections (Issue #3704)
 * Ignore ``.DS_Store`` files in listing indexes (Issue #3698)
 * Fix baguetteBox.js invoking in the base theme (Issue #3687)
@@ -16,6 +21,14 @@ Bugfixes
   for non-root SITE_URL, in particular when URL_TYPE is full_path.
   (Issue #3715)
 
+For plugin developers
+---------------------
+
+Nikola now requires the ``.plugin`` file to contain a ``[Nikola]``
+section with a ``PluginCategory`` entry set to the name of the plugin
+category class. This was already required by ``plugins.getnikola.com``,
+but you may have custom plugins that don’t have this set.
+
 New in v8.2.4
 =============
 
diff --git a/docs/internals.rst b/docs/internals.rst
index 0180f0d395..a3b7af2fca 100644
--- a/docs/internals.rst
+++ b/docs/internals.rst
@@ -15,7 +15,7 @@ So, this is a short document explaining what each piece of Nikola does and
 how it all fits together.
 
 Nikola is a Pile of Plugins
-    Most of Nikola is implemented as plugins using `Yapsy <http://yapsy.sourceforge.net/>`_.
+    Most of Nikola is implemented as plugins (using a custom plugin manager inspired by Yapsy).
     You can ignore that they are plugins and just think of them as regular python
     modules and packages with a funny little ``.plugin`` file next to them.
 
@@ -65,7 +65,7 @@ basename:name
 
    If you ever want to do your own tasks, you really should read the doit
    `documentation on tasks <https://pydoit.org/tasks.html>`_.
-   
+
    Notably, by default doit redirects ``stdout`` and ``stderr``. To get a
    proper PDB debugging shell, you need to use doit's own
    `set_trace <https://pydoit.org/tools.html#set-trace>`_ function.
diff --git a/nikola/nikola.py b/nikola/nikola.py
index 056f606dd6..dd39e82d93 100644
--- a/nikola/nikola.py
+++ b/nikola/nikola.py
@@ -35,6 +35,7 @@
 import os
 import pathlib
 import sys
+import typing
 import mimetypes
 from collections import defaultdict
 from copy import copy
@@ -47,27 +48,14 @@
 import PyRSS2Gen as rss
 from pkg_resources import resource_filename
 from blinker import signal
-from yapsy.PluginManager import PluginManager
 
 from . import DEBUG, SHOW_TRACEBACKS, filters, utils, hierarchy_utils, shortcodes
 from . import metadata_extractors
 from .metadata_extractors import default_metadata_extractors_by
 from .post import Post  # NOQA
+from .plugin_manager import PluginCandidate, PluginInfo, PluginManager
 from .plugin_categories import (
-    Command,
-    LateTask,
-    PageCompiler,
-    CompilerExtension,
-    MarkdownExtension,
-    RestExtension,
-    MetadataExtractor,
-    ShortcodePlugin,
-    Task,
-    TaskMultiplier,
     TemplateSystem,
-    SignalHandler,
-    ConfigPlugin,
-    CommentSystem,
     PostScanner,
     Taxonomy,
 )
@@ -377,25 +365,15 @@ def _enclosure(post, lang):
         return url, length, mime
 
 
-def _plugin_load_callback(plugin_info):
-    """Set the plugin's module path.
-
-    So we can find its template path later.
-    """
-    try:
-        plugin_info.plugin_object.set_module_path(plugin_info.path)
-    except AttributeError:
-        # this is just for safety in case plugin_object somehow
-        # isn't set
-        pass
-
-
 class Nikola(object):
     """Class that handles site generation.
 
     Takes a site config as argument on creation.
     """
 
+    plugin_manager: PluginManager
+    _template_system: TemplateSystem
+
     def __init__(self, **config):
         """Initialize proper environment for running tasks."""
         # Register our own path handlers
@@ -1019,57 +997,47 @@ def __init__(self, **config):
         # WebP files have no official MIME type yet, but we need to recognize them (Issue #3671)
         mimetypes.add_type('image/webp', '.webp')
 
-    def _filter_duplicate_plugins(self, plugin_list):
+    def _filter_duplicate_plugins(self, plugin_list: typing.Iterable[PluginCandidate]):
         """Find repeated plugins and discard the less local copy."""
-        def plugin_position_in_places(plugin):
+        def plugin_position_in_places(plugin: PluginInfo):
             # plugin here is a tuple:
             # (path to the .plugin file, path to plugin module w/o .py, plugin metadata)
             for i, place in enumerate(self._plugin_places):
-                if plugin[0].startswith(place):
+                place: pathlib.Path
+                try:
+                    # Path.is_relative_to backport
+                    plugin.source_dir.relative_to(place)
                     return i
-            utils.LOGGER.warn("Duplicate plugin found in unexpected location: {}".format(plugin[0]))
+                except ValueError:
+                    pass
+            utils.LOGGER.warning("Duplicate plugin found in unexpected location: {}".format(plugin.source_dir))
             return len(self._plugin_places)
 
         plugin_dict = defaultdict(list)
-        for data in plugin_list:
-            plugin_dict[data[2].name].append(data)
+        for plugin in plugin_list:
+            plugin_dict[plugin.name].append(plugin)
         result = []
-        for _, plugins in plugin_dict.items():
+        for name, plugins in plugin_dict.items():
             if len(plugins) > 1:
                 # Sort by locality
                 plugins.sort(key=plugin_position_in_places)
                 utils.LOGGER.debug("Plugin {} exists in multiple places, using {}".format(
-                    plugins[-1][2].name, plugins[-1][0]))
+                    name, plugins[-1].source_dir))
             result.append(plugins[-1])
         return result
 
     def init_plugins(self, commands_only=False, load_all=False):
         """Load plugins as needed."""
-        self.plugin_manager = PluginManager(categories_filter={
-            "Command": Command,
-            "Task": Task,
-            "LateTask": LateTask,
-            "TemplateSystem": TemplateSystem,
-            "PageCompiler": PageCompiler,
-            "TaskMultiplier": TaskMultiplier,
-            "CompilerExtension": CompilerExtension,
-            "MarkdownExtension": MarkdownExtension,
-            "RestExtension": RestExtension,
-            "MetadataExtractor": MetadataExtractor,
-            "ShortcodePlugin": ShortcodePlugin,
-            "SignalHandler": SignalHandler,
-            "ConfigPlugin": ConfigPlugin,
-            "CommentSystem": CommentSystem,
-            "PostScanner": PostScanner,
-            "Taxonomy": Taxonomy,
-        })
-        self.plugin_manager.getPluginLocator().setPluginInfoExtension('plugin')
         extra_plugins_dirs = self.config['EXTRA_PLUGINS_DIRS']
+        self._loading_commands_only = commands_only
         self._plugin_places = [
             resource_filename('nikola', 'plugins'),
             os.path.expanduser(os.path.join('~', '.nikola', 'plugins')),
             os.path.join(os.getcwd(), 'plugins'),
         ] + [path for path in extra_plugins_dirs if path]
+        self._plugin_places = [pathlib.Path(p) for p in self._plugin_places]
+
+        self.plugin_manager = PluginManager(plugin_places=self._plugin_places)
 
         compilers = defaultdict(set)
         # Also add aliases for combinations with TRANSLATIONS_PATTERN
@@ -1088,41 +1056,37 @@ def init_plugins(self, commands_only=False, load_all=False):
         self.disabled_compilers = {}
         self.disabled_compiler_extensions = defaultdict(list)
 
-        self.plugin_manager.getPluginLocator().setPluginPlaces(self._plugin_places)
-        self.plugin_manager.locatePlugins()
-        bad_candidates = set([])
+        candidates = self.plugin_manager.locate_plugins()
+        good_candidates = set()
         if not load_all:
-            for p in self.plugin_manager._candidates:
+            for p in candidates:
                 if commands_only:
-                    if p[-1].details.has_option('Nikola', 'PluginCategory'):
-                        # FIXME TemplateSystem should not be needed
-                        if p[-1].details.get('Nikola', 'PluginCategory') not in {'Command', 'Template'}:
-                            bad_candidates.add(p)
-                    else:
-                        bad_candidates.add(p)
+                    if p.category != 'Command':
+                        continue
                 elif self.configured:  # Not commands-only, and configured
                     # Remove blacklisted plugins
-                    if p[-1].name in self.config['DISABLED_PLUGINS']:
-                        bad_candidates.add(p)
-                        utils.LOGGER.debug('Not loading disabled plugin {}', p[-1].name)
-                    # Remove compilers we don't use
-                    if p[-1].details.has_option('Nikola', 'PluginCategory') and p[-1].details.get('Nikola', 'PluginCategory') in ('Compiler', 'PageCompiler'):
-                        bad_candidates.add(p)
-                        self.disabled_compilers[p[-1].name] = p
+                    if p.name in self.config['DISABLED_PLUGINS']:
+                        utils.LOGGER.debug('Not loading disabled plugin {}', p.name)
+                        continue
+                    # Remove compilers - will be loaded later based on usage
+                    if p.category == "PageCompiler":
+                        self.disabled_compilers[p.name] = p
+                        continue
                     # Remove compiler extensions we don't need
-                    if p[-1].details.has_option('Nikola', 'compiler') and p[-1].details.get('Nikola', 'compiler') in self.disabled_compilers:
-                        bad_candidates.add(p)
-                        self.disabled_compiler_extensions[p[-1].details.get('Nikola', 'compiler')].append(p)
-            self.plugin_manager._candidates = list(set(self.plugin_manager._candidates) - bad_candidates)
+                    if p.compiler and p.compiler in self.disabled_compilers:
+                        self.disabled_compiler_extensions[p.compiler].append(p)
+                        continue
+                good_candidates.add(p)
 
-        self.plugin_manager._candidates = self._filter_duplicate_plugins(self.plugin_manager._candidates)
-        self.plugin_manager.loadPlugins(callback_after=_plugin_load_callback)
+        good_candidates = self._filter_duplicate_plugins(good_candidates)
+        self.plugin_manager.load_plugins(good_candidates)
 
         # Search for compiler plugins which we disabled but shouldn't have
         self._activate_plugins_of_category("PostScanner")
         if not load_all:
             file_extensions = set()
-            for post_scanner in [p.plugin_object for p in self.plugin_manager.getPluginsOfCategory('PostScanner')]:
+            for post_scanner in [p.plugin_object for p in self.plugin_manager.get_plugins_of_category('PostScanner')]:
+                post_scanner: PostScanner
                 exts = post_scanner.supported_extensions()
                 if exts is not None:
                     file_extensions.update(exts)
@@ -1141,13 +1105,13 @@ def init_plugins(self, commands_only=False, load_all=False):
                     for p in self.disabled_compiler_extensions.pop(k, []):
                         to_add.append(p)
             for _, p in self.disabled_compilers.items():
-                utils.LOGGER.debug('Not loading unneeded compiler {}', p[-1].name)
+                utils.LOGGER.debug('Not loading unneeded compiler %s', p.name)
             for _, plugins in self.disabled_compiler_extensions.items():
                 for p in plugins:
-                    utils.LOGGER.debug('Not loading compiler extension {}', p[-1].name)
+                    utils.LOGGER.debug('Not loading compiler extension %s', p.name)
             if to_add:
-                self.plugin_manager._candidates = self._filter_duplicate_plugins(to_add)
-                self.plugin_manager.loadPlugins(callback_after=_plugin_load_callback)
+                extra_candidates = self._filter_duplicate_plugins(to_add)
+                self.plugin_manager.load_plugins(extra_candidates)
 
         # Jupyter theme configuration.  If a website has ipynb enabled in post_pages
         # we should enable the Jupyter CSS (leaving that up to the theme itself).
@@ -1160,7 +1124,8 @@ def init_plugins(self, commands_only=False, load_all=False):
 
         self._activate_plugins_of_category("Taxonomy")
         self.taxonomy_plugins = {}
-        for taxonomy in [p.plugin_object for p in self.plugin_manager.getPluginsOfCategory('Taxonomy')]:
+        for taxonomy in [p.plugin_object for p in self.plugin_manager.get_plugins_of_category('Taxonomy')]:
+            taxonomy: Taxonomy
             if not taxonomy.is_enabled():
                 continue
             if taxonomy.classification_name in self.taxonomy_plugins:
@@ -1186,10 +1151,9 @@ def init_plugins(self, commands_only=False, load_all=False):
 
         # Activate all required compiler plugins
         self.compiler_extensions = self._activate_plugins_of_category("CompilerExtension")
-        for plugin_info in self.plugin_manager.getPluginsOfCategory("PageCompiler"):
+        for plugin_info in self.plugin_manager.get_plugins_of_category("PageCompiler"):
             if plugin_info.name in self.config["COMPILERS"].keys():
-                self.plugin_manager.activatePluginByName(plugin_info.name)
-                plugin_info.plugin_object.set_site(self)
+                self._activate_plugin(plugin_info)
 
         # Activate shortcode plugins
         self._activate_plugins_of_category("ShortcodePlugin")
@@ -1198,10 +1162,8 @@ def init_plugins(self, commands_only=False, load_all=False):
         self.compilers = {}
         self.inverse_compilers = {}
 
-        for plugin_info in self.plugin_manager.getPluginsOfCategory(
-                "PageCompiler"):
-            self.compilers[plugin_info.name] = \
-                plugin_info.plugin_object
+        for plugin_info in self.plugin_manager.get_plugins_of_category("PageCompiler"):
+            self.compilers[plugin_info.name] = plugin_info.plugin_object
 
         # Load comment systems, config plugins and register templated shortcodes
         self._activate_plugins_of_category("CommentSystem")
@@ -1344,13 +1306,26 @@ def _set_all_page_deps_from_config(self):
         self.ALL_PAGE_DEPS['index_read_more_link'] = self.config.get('INDEX_READ_MORE_LINK')
         self.ALL_PAGE_DEPS['feed_read_more_link'] = self.config.get('FEED_READ_MORE_LINK')
 
-    def _activate_plugins_of_category(self, category):
+    def _activate_plugin(self, plugin_info: PluginInfo) -> None:
+        plugin_info.plugin_object.set_site(self)
+
+        if plugin_info.category == "TemplateSystem" or self._loading_commands_only:
+            return
+
+        templates_directory_candidates = [
+            plugin_info.source_dir / "templates" / self.template_system.name,
+            plugin_info.source_dir / plugin_info.module_name / "templates" / self.template_system.name
+        ]
+        for candidate in templates_directory_candidates:
+            if candidate.exists() and candidate.is_dir():
+                self.template_system.inject_directory(str(candidate))
+
+    def _activate_plugins_of_category(self, category) -> typing.List[PluginInfo]:
         """Activate all the plugins of a given category and return them."""
         # this code duplicated in tests/base.py
         plugins = []
-        for plugin_info in self.plugin_manager.getPluginsOfCategory(category):
-            self.plugin_manager.activatePluginByName(plugin_info.name)
-            plugin_info.plugin_object.set_site(self)
+        for plugin_info in self.plugin_manager.get_plugins_of_category(category):
+            self._activate_plugin(plugin_info)
             plugins.append(plugin_info)
         return plugins
 
@@ -1414,13 +1389,12 @@ def _get_template_system(self):
         if self._template_system is None:
             # Load template plugin
             template_sys_name = utils.get_template_engine(self.THEMES)
-            pi = self.plugin_manager.getPluginByName(
-                template_sys_name, "TemplateSystem")
+            pi = self.plugin_manager.get_plugin_by_name(template_sys_name, "TemplateSystem")
             if pi is None:
                 sys.stderr.write("Error loading {0} template system "
                                  "plugin\n".format(template_sys_name))
                 sys.exit(1)
-            self._template_system = pi.plugin_object
+            self._template_system = typing.cast(TemplateSystem, pi.plugin_object)
             lookup_dirs = ['templates'] + [os.path.join(utils.get_theme_path(name), "templates")
                                            for name in self.THEMES]
             self._template_system.set_directories(lookup_dirs,
@@ -2089,7 +2063,7 @@ def flatten(task):
                         yield ft
 
         task_dep = []
-        for pluginInfo in self.plugin_manager.getPluginsOfCategory(plugin_category):
+        for pluginInfo in self.plugin_manager.get_plugins_of_category(plugin_category):
             for task in flatten(pluginInfo.plugin_object.gen_tasks()):
                 if 'basename' not in task:
                     raise ValueError("Task {0} does not have a basename".format(task))
@@ -2098,7 +2072,7 @@ def flatten(task):
                     task['task_dep'] = []
                 task['task_dep'].extend(self.injected_deps[task['basename']])
                 yield task
-                for multi in self.plugin_manager.getPluginsOfCategory("TaskMultiplier"):
+                for multi in self.plugin_manager.get_plugins_of_category("TaskMultiplier"):
                     flag = False
                     for task in multi.plugin_object.process(task, name):
                         flag = True
@@ -2207,7 +2181,7 @@ def scan_posts(self, really=False, ignore_quit=False, quiet=False):
         self.timeline = []
         self.pages = []
 
-        for p in sorted(self.plugin_manager.getPluginsOfCategory('PostScanner'), key=operator.attrgetter('name')):
+        for p in sorted(self.plugin_manager.get_plugins_of_category('PostScanner'), key=operator.attrgetter('name')):
             try:
                 timeline = p.plugin_object.scan()
             except Exception:
diff --git a/nikola/plugin_categories.py b/nikola/plugin_categories.py
index 08316284d5..980f9106a9 100644
--- a/nikola/plugin_categories.py
+++ b/nikola/plugin_categories.py
@@ -33,7 +33,6 @@
 
 import doit
 from doit.cmd_base import Command as DoitCommand
-from yapsy.IPlugin import IPlugin
 
 from .utils import LOGGER, first_line, get_logger, req_missing
 
@@ -58,7 +57,7 @@
 )
 
 
-class BasePlugin(IPlugin):
+class BasePlugin:
     """Base plugin class."""
 
     logger = None
@@ -66,7 +65,6 @@ class BasePlugin(IPlugin):
     def set_site(self, site):
         """Set site, which is a Nikola instance."""
         self.site = site
-        self.inject_templates()
         self.logger = get_logger(self.name)
         if not site.debug:
             self.logger.level = logging.INFO
@@ -75,21 +73,6 @@ def set_module_path(self, module_path):
         """Set the plugin's module path."""
         self.module_path = module_path
 
-    def inject_templates(self):
-        """Inject 'templates/<engine>' (if exists) very early in the theme chain."""
-        try:
-            mod_dir = os.path.dirname(self.module_path)
-            tmpl_dir = os.path.join(
-                mod_dir, 'templates', self.site.template_system.name
-            )
-            if os.path.isdir(tmpl_dir):
-                # Inject tmpl_dir low in the theme chain
-                self.site.template_system.inject_directory(tmpl_dir)
-        except AttributeError:
-            # This would likely mean we don't have module_path set.
-            # this should not usually happen, so log a warning
-            LOGGER.warning("Could not find template path for module {0}".format(self.name))
-
     def inject_dependency(self, target, dependency):
         """Add 'dependency' to the target task's task_deps."""
         self.site.injected_deps[target].append(dependency)
@@ -359,7 +342,7 @@ def get_compiler_extensions(self) -> list:
         """Activate all the compiler extension plugins for a given compiler and return them."""
         plugins = []
         for plugin_info in self.site.compiler_extensions:
-            if plugin_info.plugin_object.compiler_name == self.name:
+            if plugin_info.compiler == self.name or plugin_info.plugin_object.compiler_name == self.name:
                 plugins.append(plugin_info)
         return plugins
 
@@ -371,11 +354,8 @@ class CompilerExtension(BasePlugin):
     (a) create a new plugin class for them; or
     (b) use this class and filter them yourself.
     If you choose (b), you should the compiler name to the .plugin
-    file in the Nikola/Compiler section and filter all plugins of
-    this category, getting the compiler name with:
-        p.details.get('Nikola', 'Compiler')
-    Note that not all compiler plugins have this option and you might
-    need to catch configparser.NoOptionError exceptions.
+    file in the Nikola/compiler section and filter all plugins of
+    this category, getting the compiler name with `plugin_info.compiler`.
     """
 
     name = "dummy_compiler_extension"
@@ -904,3 +884,23 @@ def get_other_language_variants(self, classification: str, lang: str, classifica
         Provided is a set of classifications per language (`classifications_per_language`).
         """
         return []
+
+
+CATEGORIES = {
+    "Command": Command,
+    "Task": Task,
+    "LateTask": LateTask,
+    "TemplateSystem": TemplateSystem,
+    "PageCompiler": PageCompiler,
+    "TaskMultiplier": TaskMultiplier,
+    "CompilerExtension": CompilerExtension,
+    "MarkdownExtension": MarkdownExtension,
+    "RestExtension": RestExtension,
+    "MetadataExtractor": MetadataExtractor,
+    "ShortcodePlugin": ShortcodePlugin,
+    "SignalHandler": SignalHandler,
+    "ConfigPlugin": ConfigPlugin,
+    "CommentSystem": CommentSystem,
+    "PostScanner": PostScanner,
+    "Taxonomy": Taxonomy,
+}
diff --git a/nikola/plugin_manager.py b/nikola/plugin_manager.py
new file mode 100644
index 0000000000..5c1a29a103
--- /dev/null
+++ b/nikola/plugin_manager.py
@@ -0,0 +1,264 @@
+# -*- coding: utf-8 -*-
+
+# Copyright © 2012-2024 Chris Warrick and others.
+
+# Permission is hereby granted, free of charge, to any
+# person obtaining a copy of this software and associated
+# documentation files (the "Software"), to deal in the
+# Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the
+# Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice
+# shall be included in all copies or substantial portions of
+# the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+"""The Nikola plugin manager. Inspired by yapsy."""
+
+import configparser
+import importlib
+import importlib.util
+import time
+import sys
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Dict, List, Optional, Type, TYPE_CHECKING, Set
+
+from .plugin_categories import BasePlugin, CATEGORIES
+from .utils import get_logger
+
+if TYPE_CHECKING:
+    import logging
+
+LEGACY_PLUGIN_NAMES: Dict[str, str] = {
+    "Compiler": "PageCompiler",
+    "Shortcode": "ShortcodePlugin",
+    "Template": "TemplateSystem",
+}
+
+CATEGORY_NAMES: Set[str] = set(CATEGORIES.keys())
+CATEGORY_TYPES: Set[Type[BasePlugin]] = set(CATEGORIES.values())
+
+
+@dataclass(frozen=True)
+class PluginCandidate:
+    """A candidate plugin that was located but not yet loaded (imported)."""
+
+    name: str
+    description: Optional[str]
+    plugin_id: str
+    category: str
+    compiler: Optional[str]
+    source_dir: Path
+    module_name: str
+
+
+@dataclass(frozen=True)
+class PluginInfo:
+    """A plugin that was loaded (imported)."""
+
+    name: str
+    description: Optional[str]
+    plugin_id: str
+    category: str
+    compiler: Optional[str]
+    source_dir: Path
+    module_name: str
+    module_object: object
+    plugin_object: BasePlugin
+
+
+class PluginManager:
+    """The Nikola plugin manager."""
+
+    categories_filter: Dict[str, Type[BasePlugin]]
+    plugin_places: List[Path]
+    logger: "logging.Logger"
+    candidates: List[PluginCandidate]
+    plugins: List[PluginInfo]
+    _plugins_by_category: Dict[str, List[PluginInfo]]
+    has_warnings: bool = False
+
+    def __init__(self, plugin_places: List[Path]):
+        """Initialize the plugin manager."""
+        self.plugin_places = plugin_places
+        self.candidates = []
+        self.plugins = []
+        self._plugins_by_category = {}
+        self.logger = get_logger("PluginManager")
+
+    def locate_plugins(self) -> List[PluginCandidate]:
+        """Locate plugins in plugin_places."""
+        self.candidates = []
+
+        plugin_files: List[Path] = []
+        for place in self.plugin_places:
+            plugin_files += place.rglob("*.plugin")
+
+        for plugin_file in plugin_files:
+            source_dir = plugin_file.parent
+            config = configparser.ConfigParser()
+            config.read(plugin_file)
+            name = config["Core"]["name"]
+            module_name = config["Core"]["module"]
+            plugin_id = f"Plugin {name} from {plugin_file}"
+            description = None
+            if "Documentation" in config:
+                description = config["Documentation"].get("Description")
+            if "Nikola" not in config:
+                self.logger.warning(f"{plugin_id} does not specify Nikola configuration - plugin will not be loaded")
+                self.logger.warning("Please add a [Nikola] section to the {plugin_file} file with a PluginCategory entry")
+                self.has_warnings = True
+                continue
+            category = config["Nikola"].get("PluginCategory")
+            compiler = config["Nikola"].get("Compiler")
+            if not category:
+                self.logger.warning(f"{plugin_id} does not specify any category (Nikola.PluginCategory is missing in .plugin file) - plugin will not be loaded")
+                self.has_warnings = True
+                continue
+            if category in LEGACY_PLUGIN_NAMES:
+                category = LEGACY_PLUGIN_NAMES[category]
+            if category not in CATEGORY_NAMES:
+                self.logger.warning(f"{plugin_id} specifies invalid category '{category}' in the .plugin file - plugin will not be loaded")
+                self.has_warnings = True
+                continue
+            self.logger.debug(f"Discovered {plugin_id}")
+            self.candidates.append(
+                PluginCandidate(
+                    name=name,
+                    description=description,
+                    plugin_id=plugin_id,
+                    category=category,
+                    compiler=compiler,
+                    source_dir=source_dir,
+                    module_name=module_name,
+                )
+            )
+        return self.candidates
+
+    def load_plugins(self, candidates: List[PluginCandidate]) -> None:
+        """Load selected candidate plugins."""
+        plugins_root = Path(__file__).parent.parent
+
+        for candidate in candidates:
+            name = candidate.name
+            module_name = candidate.module_name
+            source_dir = candidate.source_dir
+            py_file_location = source_dir / f"{module_name}.py"
+            plugin_id = candidate.plugin_id
+            if not py_file_location.exists():
+                py_file_location = source_dir / module_name / "__init__.py"
+            if not py_file_location.exists():
+                self.logger.warning(f"{plugin_id} could not be loaded (no valid module detected)")
+                self.has_warnings = True
+                continue
+
+            plugin_id += f" ({py_file_location})"
+            full_module_name = module_name
+
+            try:
+                name_parts = list(py_file_location.relative_to(plugins_root).parts)
+                if name_parts[-1] == "__init__.py":
+                    name_parts.pop(-1)
+                elif name_parts[-1].endswith(".py"):
+                    name_parts[-1] = name_parts[-1][:-3]
+                full_module_name = ".".join(name_parts)
+            except ValueError:
+                pass
+
+            try:
+                spec = importlib.util.spec_from_file_location(full_module_name, py_file_location)
+                module_object = importlib.util.module_from_spec(spec)
+                if full_module_name not in sys.modules:
+                    sys.modules[full_module_name] = module_object
+                spec.loader.exec_module(module_object)
+            except Exception:
+                self.logger.exception(f"{plugin_id} threw an exception while loading")
+                self.has_warnings = True
+                continue
+
+            plugin_classes = [
+                c
+                for c in vars(module_object).values()
+                if isinstance(c, type) and issubclass(c, BasePlugin) and c not in CATEGORY_TYPES
+            ]
+            if len(plugin_classes) == 0:
+                self.logger.warning(f"{plugin_id} does not have any plugin classes - plugin will not be loaded")
+                self.has_warnings = True
+                continue
+            elif len(plugin_classes) > 1:
+                self.logger.warning(f"{plugin_id} has multiple plugin classes; this is not supported - plugin will not be loaded")
+                self.has_warnings = True
+                continue
+
+            plugin_class = plugin_classes[0]
+
+            if not issubclass(plugin_class, CATEGORIES[candidate.category]):
+                self.logger.warning(f"{plugin_id} has category '{candidate.category}' in the .plugin file, but the implementation class {plugin_class} does not inherit from this category - plugin will not be loaded")
+                self.has_warnings = True
+                continue
+
+            try:
+                plugin_object = plugin_class()
+            except Exception:
+                self.logger.exception(f"{plugin_id} threw an exception while creating the instance")
+                self.has_warnings = True
+                continue
+            self.logger.debug(f"Loaded {plugin_id}")
+            info = PluginInfo(
+                name=name,
+                description=candidate.description,
+                plugin_id=candidate.plugin_id,
+                category=candidate.category,
+                compiler=candidate.compiler,
+                source_dir=source_dir,
+                module_name=module_name,
+                module_object=module_object,
+                plugin_object=plugin_object,
+            )
+            self.plugins.append(info)
+
+        self._plugins_by_category = {category: [] for category in CATEGORY_NAMES}
+        for plugin_info in self.plugins:
+            self._plugins_by_category[plugin_info.category].append(plugin_info)
+
+        if self.has_warnings:
+            self.logger.warning("Some plugins failed to load. Please review the above warning messages.")
+            # TODO remove following messages and delay in v8.3.1
+            self.logger.warning("You may need to update some plugins (from plugins.getnikola.com) or to fix their .plugin files.")
+            self.logger.warning("Waiting 2 seconds before continuing.")
+            time.sleep(2)
+
+    def get_plugins_of_category(self, category: str) -> List[PluginInfo]:
+        """Get loaded plugins of a given category."""
+        return self._plugins_by_category.get(category, [])
+
+    def get_plugin_by_name(self, name: str, category: Optional[str] = None) -> Optional[PluginInfo]:
+        """Get a loaded plugin by name and optionally by category. Returns None if no such plugin is loaded."""
+        for p in self.plugins:
+            if p.name == name and (category is None or p.category == category):
+                return p
+
+    # Aliases for Yapsy compatibility
+    # TODO: remove in v9
+    def getPluginsOfCategory(self, category: str) -> List[PluginInfo]:
+        """Get loaded plugins of a given category."""
+        self.logger.warning("Legacy getPluginsOfCategory method was used, it may be removed in the future. Please change it to get_plugins_of_category.")
+        return self._plugins_by_category.get(category, [])
+
+    # TODO: remove in v9
+    def getPluginByName(self, name: str, category: Optional[str] = None) -> Optional[PluginInfo]:
+        """Get a loaded plugin by name and optionally by category. Returns None if no such plugin is loaded."""
+        self.logger.warning("Legacy getPluginByName method was used, it may be removed in the future. Please change it to get_plugin_by_name.")
+        return self.get_plugin_by_name(name, category)
diff --git a/nikola/plugins/command/import_wordpress.py b/nikola/plugins/command/import_wordpress.py
index e419c8a1b7..27f58b0da6 100644
--- a/nikola/plugins/command/import_wordpress.py
+++ b/nikola/plugins/command/import_wordpress.py
@@ -66,7 +66,7 @@ def install_plugin(site, plugin_name, output_dir=None, show_install_notes=False)
     """Install a Nikola plugin."""
     LOGGER.info("Installing plugin '{0}'".format(plugin_name))
     # Get hold of the 'plugin' plugin
-    plugin_installer_info = site.plugin_manager.getPluginByName('plugin', 'Command')
+    plugin_installer_info = site.plugin_manager.get_plugin_by_name('plugin', 'Command')
     if plugin_installer_info is None:
         LOGGER.error('Internal error: cannot find the "plugin" plugin which is supposed to come with Nikola!')
         return False
@@ -236,10 +236,9 @@ def _get_compiler(self):
         self._find_wordpress_compiler()
         if self.wordpress_page_compiler is not None:
             return self.wordpress_page_compiler
-        plugin_info = self.site.plugin_manager.getPluginByName('markdown', 'PageCompiler')
+        plugin_info = self.site.plugin_manager.get_plugin_by_name('markdown', 'PageCompiler')
         if plugin_info is not None:
             if not plugin_info.is_activated:
-                self.site.plugin_manager.activatePluginByName(plugin_info.name)
                 plugin_info.plugin_object.set_site(self.site)
             return plugin_info.plugin_object
         else:
@@ -249,7 +248,7 @@ def _find_wordpress_compiler(self):
         """Find WordPress compiler plugin."""
         if self.wordpress_page_compiler is not None:
             return
-        plugin_info = self.site.plugin_manager.getPluginByName('wordpress', 'PageCompiler')
+        plugin_info = self.site.plugin_manager.get_plugin_by_name('wordpress', 'PageCompiler')
         if plugin_info is not None:
             if not plugin_info.is_activated:
                 self.site.plugin_manager.activatePluginByName(plugin_info.name)
diff --git a/nikola/plugins/command/new_page.py b/nikola/plugins/command/new_page.py
index cde5e5c6c6..780e5db2ff 100644
--- a/nikola/plugins/command/new_page.py
+++ b/nikola/plugins/command/new_page.py
@@ -109,5 +109,5 @@ def _execute(self, options, args):
         options['date-path'] = False
         # Even though stuff was split into `new_page`, it’s easier to do it
         # there not to duplicate the code.
-        p = self.site.plugin_manager.getPluginByName('new_post', 'Command').plugin_object
+        p = self.site.plugin_manager.get_plugin_by_name('new_post', 'Command').plugin_object
         return p.execute(options, args)
diff --git a/nikola/plugins/command/new_post.py b/nikola/plugins/command/new_post.py
index 45ca1a11f8..2c03fa5c73 100644
--- a/nikola/plugins/command/new_post.py
+++ b/nikola/plugins/command/new_post.py
@@ -216,9 +216,7 @@ class CommandNewPost(Command):
     def _execute(self, options, args):
         """Create a new post or page."""
         global LOGGER
-        compiler_names = [p.name for p in
-                          self.site.plugin_manager.getPluginsOfCategory(
-                              "PageCompiler")]
+        compiler_names = [p.name for p in self.site.plugin_manager.get_plugins_of_category("PageCompiler")]
 
         if len(args) > 1:
             print(self.help())
@@ -298,7 +296,7 @@ def _execute(self, options, args):
             self.print_compilers()
             return
 
-        compiler_plugin = self.site.plugin_manager.getPluginByName(
+        compiler_plugin = self.site.plugin_manager.get_plugin_by_name(
             content_format, "PageCompiler").plugin_object
 
         # Guess where we should put this
diff --git a/nikola/plugins/command/rst2html/__init__.py b/nikola/plugins/command/rst2html/__init__.py
index a133bd5ec8..d2854df94b 100644
--- a/nikola/plugins/command/rst2html/__init__.py
+++ b/nikola/plugins/command/rst2html/__init__.py
@@ -44,7 +44,7 @@ class CommandRst2Html(Command):
 
     def _execute(self, options, args):
         """Compile reStructuredText to standalone HTML files."""
-        compiler = self.site.plugin_manager.getPluginByName('rest', 'PageCompiler').plugin_object
+        compiler = self.site.plugin_manager.get_plugin_by_name('rest', 'PageCompiler').plugin_object
         if len(args) != 1:
             print("This command takes only one argument (input file name).")
             return 2
diff --git a/nikola/plugins/compile/pandoc.py b/nikola/plugins/compile/pandoc.py
index c79c4d88e7..f510256179 100644
--- a/nikola/plugins/compile/pandoc.py
+++ b/nikola/plugins/compile/pandoc.py
@@ -62,10 +62,10 @@ def _get_pandoc_options(self, source: str) -> List[str]:
             try:
                 pandoc_options = list(config_options[ext])
             except KeyError:
-                self.logger.warn('Setting PANDOC_OPTIONS to [], because extension {} is not defined in PANDOC_OPTIONS: {}.'.format(ext, config_options))
+                self.logger.warning('Setting PANDOC_OPTIONS to [], because extension {} is not defined in PANDOC_OPTIONS: {}.'.format(ext, config_options))
                 pandoc_options = []
         else:
-            self.logger.warn('Setting PANDOC_OPTIONS to [], because PANDOC_OPTIONS is expected to be of type Union[List[str], Dict[str, List[str]]] but this is not: {}'.format(config_options))
+            self.logger.warning('Setting PANDOC_OPTIONS to [], because PANDOC_OPTIONS is expected to be of type Union[List[str], Dict[str, List[str]]] but this is not: {}'.format(config_options))
             pandoc_options = []
         return pandoc_options
 
diff --git a/nikola/plugins/compile/rest/chart.py b/nikola/plugins/compile/rest/chart.py
index d217c1bf2e..558fe7c904 100644
--- a/nikola/plugins/compile/rest/chart.py
+++ b/nikola/plugins/compile/rest/chart.py
@@ -153,7 +153,7 @@ class Chart(Directive):
     def run(self):
         """Run the directive."""
         self.options['site'] = None
-        html = _site.plugin_manager.getPluginByName(
+        html = _site.plugin_manager.get_plugin_by_name(
             'chart', 'ShortcodePlugin').plugin_object.handler(
                 self.arguments[0],
                 data='\n'.join(self.content),
diff --git a/nikola/plugins/compile/rest/post_list.py b/nikola/plugins/compile/rest/post_list.py
index f5b86baef2..9f66073643 100644
--- a/nikola/plugins/compile/rest/post_list.py
+++ b/nikola/plugins/compile/rest/post_list.py
@@ -88,7 +88,7 @@ def run(self):
         date = self.options.get('date')
         filename = self.state.document.settings._nikola_source_path
 
-        output, deps = self.site.plugin_manager.getPluginByName(
+        output, deps = self.site.plugin_manager.get_plugin_by_name(
             'post_list', 'ShortcodePlugin').plugin_object.handler(
                 start,
                 stop,
diff --git a/nikola/plugins/misc/scan_posts.plugin b/nikola/plugins/misc/scan_posts.plugin
index f4af811276..0fb946c792 100644
--- a/nikola/plugins/misc/scan_posts.plugin
+++ b/nikola/plugins/misc/scan_posts.plugin
@@ -8,3 +8,5 @@ Version = 1.0
 Website = https://getnikola.com/
 Description = Scan posts and create timeline
 
+[Nikola]
+PluginCategory = PostScanner
diff --git a/nikola/plugins/shortcode/chart.plugin b/nikola/plugins/shortcode/chart.plugin
index edcbc1310a..be1fbc6efd 100644
--- a/nikola/plugins/shortcode/chart.plugin
+++ b/nikola/plugins/shortcode/chart.plugin
@@ -3,7 +3,7 @@ name = chart
 module = chart
 
 [Nikola]
-PluginCategory = Shortcode
+PluginCategory = ShortcodePlugin
 
 [Documentation]
 author = Roberto Alsina
diff --git a/nikola/plugins/shortcode/emoji.plugin b/nikola/plugins/shortcode/emoji.plugin
index c9a272cdcd..4c09f03157 100644
--- a/nikola/plugins/shortcode/emoji.plugin
+++ b/nikola/plugins/shortcode/emoji.plugin
@@ -3,7 +3,7 @@ name = emoji
 module = emoji
 
 [Nikola]
-PluginCategory = Shortcode
+PluginCategory = ShortcodePlugin
 
 [Documentation]
 author = Roberto Alsina
diff --git a/nikola/plugins/shortcode/gist.plugin b/nikola/plugins/shortcode/gist.plugin
index b610763835..ee62c27069 100644
--- a/nikola/plugins/shortcode/gist.plugin
+++ b/nikola/plugins/shortcode/gist.plugin
@@ -3,7 +3,7 @@ name = gist
 module = gist
 
 [Nikola]
-PluginCategory = Shortcode
+PluginCategory = ShortcodePlugin
 
 [Documentation]
 author = Roberto Alsina
diff --git a/nikola/plugins/shortcode/listing.plugin b/nikola/plugins/shortcode/listing.plugin
index 90fb6ebb28..70fa1cf416 100644
--- a/nikola/plugins/shortcode/listing.plugin
+++ b/nikola/plugins/shortcode/listing.plugin
@@ -3,7 +3,7 @@ name = listing_shortcode
 module = listing
 
 [Nikola]
-PluginCategory = Shortcode
+PluginCategory = ShortcodePlugin
 
 [Documentation]
 author = Roberto Alsina
diff --git a/nikola/plugins/shortcode/post_list.plugin b/nikola/plugins/shortcode/post_list.plugin
index 494a1d8755..9c39eb9e99 100644
--- a/nikola/plugins/shortcode/post_list.plugin
+++ b/nikola/plugins/shortcode/post_list.plugin
@@ -3,7 +3,7 @@ name = post_list
 module = post_list
 
 [Nikola]
-PluginCategory = Shortcode
+PluginCategory = ShortcodePlugin
 
 [Documentation]
 author = Udo Spallek
diff --git a/nikola/plugins/shortcode/thumbnail.plugin b/nikola/plugins/shortcode/thumbnail.plugin
index e55d34f6c3..bd36169002 100644
--- a/nikola/plugins/shortcode/thumbnail.plugin
+++ b/nikola/plugins/shortcode/thumbnail.plugin
@@ -3,7 +3,7 @@ name = thumbnail
 module = thumbnail
 
 [Nikola]
-PluginCategory = Shortcode
+PluginCategory = ShortcodePlugin
 
 [Documentation]
 author = Chris Warrick
diff --git a/nikola/plugins/task/bundles.plugin b/nikola/plugins/task/bundles.plugin
index 939065b7cb..4afc3ecd3f 100644
--- a/nikola/plugins/task/bundles.plugin
+++ b/nikola/plugins/task/bundles.plugin
@@ -9,5 +9,5 @@ website = https://getnikola.com/
 description = Bundle assets
 
 [Nikola]
-PluginCategory = Task
+PluginCategory = LateTask
 
diff --git a/nikola/plugins/task/gzip.plugin b/nikola/plugins/task/gzip.plugin
index 70e966b83a..b1aab25dc8 100644
--- a/nikola/plugins/task/gzip.plugin
+++ b/nikola/plugins/task/gzip.plugin
@@ -9,5 +9,5 @@ website = https://getnikola.com/
 description = Create gzipped copies of files
 
 [Nikola]
-PluginCategory = Task
+PluginCategory = TaskMultiplier
 
diff --git a/nikola/plugins/task/listings.py b/nikola/plugins/task/listings.py
index 4c1636e558..f4933e9379 100644
--- a/nikola/plugins/task/listings.py
+++ b/nikola/plugins/task/listings.py
@@ -113,7 +113,7 @@ def render_listing(in_name, out_name, input_folder, output_folder, folders=[], f
             needs_ipython_css = False
             if in_name and in_name.endswith('.ipynb'):
                 # Special handling: render ipynbs in listings (Issue #1900)
-                ipynb_plugin = self.site.plugin_manager.getPluginByName("ipynb", "PageCompiler")
+                ipynb_plugin = self.site.plugin_manager.get_plugin_by_name("ipynb", "PageCompiler")
                 if ipynb_plugin is None:
                     msg = "To use .ipynb files as listings, you must set up the Jupyter compiler in COMPILERS and POSTS/PAGES."
                     utils.LOGGER.error(msg)
diff --git a/nikola/plugins/task/robots.plugin b/nikola/plugins/task/robots.plugin
index 51f778183c..81c4c9a6b9 100644
--- a/nikola/plugins/task/robots.plugin
+++ b/nikola/plugins/task/robots.plugin
@@ -9,5 +9,5 @@ website = https://getnikola.com/
 description = Generate /robots.txt exclusion file and promote sitemap.
 
 [Nikola]
-PluginCategory = Task
+PluginCategory = LateTask
 
diff --git a/nikola/plugins/task/sitemap.plugin b/nikola/plugins/task/sitemap.plugin
index c8aa832392..8367d8ecaa 100644
--- a/nikola/plugins/task/sitemap.plugin
+++ b/nikola/plugins/task/sitemap.plugin
@@ -9,5 +9,5 @@ website = https://getnikola.com/
 description = Generate google sitemap.
 
 [Nikola]
-PluginCategory = Task
+PluginCategory = LateTask
 
diff --git a/nikola/plugins/task/sitemap.py b/nikola/plugins/task/sitemap.py
index bc9a5d6569..3c045eb0df 100644
--- a/nikola/plugins/task/sitemap.py
+++ b/nikola/plugins/task/sitemap.py
@@ -309,7 +309,7 @@ def get_lastmod(self, p):
             # RFC 3339 (web ISO 8601 profile) represented in UTC with Zulu
             # zone desgignator as recommeded for sitemaps. Second and
             # microsecond precision is stripped for compatibility.
-            lastmod = datetime.datetime.utcfromtimestamp(os.stat(p).st_mtime).replace(tzinfo=dateutil.tz.gettz('UTC'), second=0, microsecond=0).isoformat().replace('+00:00', 'Z')
+            lastmod = datetime.datetime.fromtimestamp(os.stat(p).st_mtime, dateutil.tz.tzutc()).replace(second=0, microsecond=0).isoformat().replace('+00:00', 'Z')
             return lastmod
 
 
diff --git a/nikola/plugins/template/jinja.plugin b/nikola/plugins/template/jinja.plugin
index 629b20e888..45dd621643 100644
--- a/nikola/plugins/template/jinja.plugin
+++ b/nikola/plugins/template/jinja.plugin
@@ -9,5 +9,5 @@ website = https://getnikola.com/
 description = Support for Jinja2 templates.
 
 [Nikola]
-PluginCategory = Template
+PluginCategory = TemplateSystem
 
diff --git a/nikola/plugins/template/mako.plugin b/nikola/plugins/template/mako.plugin
index 2d353bf1d9..a46575255e 100644
--- a/nikola/plugins/template/mako.plugin
+++ b/nikola/plugins/template/mako.plugin
@@ -9,5 +9,5 @@ website = https://getnikola.com/
 description = Support for Mako templates.
 
 [Nikola]
-PluginCategory = Template
+PluginCategory = TemplateSystem
 
diff --git a/nikola/post.py b/nikola/post.py
index 1dcd33d609..d4172d548b 100644
--- a/nikola/post.py
+++ b/nikola/post.py
@@ -350,8 +350,8 @@ def _set_date(self, default_metadata):
             if self.config['__invariant__']:
                 default_metadata['date'] = datetime.datetime(2013, 12, 31, 23, 59, 59, tzinfo=self.config['__tzinfo__'])
             else:
-                default_metadata['date'] = datetime.datetime.utcfromtimestamp(
-                    os.stat(self.source_path).st_ctime).replace(tzinfo=dateutil.tz.tzutc()).astimezone(self.config['__tzinfo__'])
+                default_metadata['date'] = datetime.datetime.fromtimestamp(
+                    os.stat(self.source_path).st_ctime, dateutil.tz.tzutc()).astimezone(self.config['__tzinfo__'])
 
         # If time zone is set, build localized datetime.
         try:
diff --git a/requirements.txt b/requirements.txt
index e4ef1a36a2..5e7f0b01b6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,7 +7,6 @@ mako>=1.0.0
 Markdown>=3.0.0
 unidecode>=0.04.16
 lxml>=3.3.5
-Yapsy>=1.12.0
 PyRSS2Gen>=1.1
 blinker>=1.3
 setuptools>=24.2.0
diff --git a/setup.py b/setup.py
index f2f5615ad8..5db7f89474 100755
--- a/setup.py
+++ b/setup.py
@@ -133,6 +133,7 @@ def run(self):
                    'Programming Language :: Python :: 3.9',
                    'Programming Language :: Python :: 3.10',
                    'Programming Language :: Python :: 3.11',
+                   'Programming Language :: Python :: 3.12',
                    'Topic :: Internet',
                    'Topic :: Internet :: WWW/HTTP',
                    'Topic :: Text Processing :: Markup'],
diff --git a/snapcraft.yaml b/snapcraft.yaml
index 50962eaa65..bd7ce8b5f8 100644
--- a/snapcraft.yaml
+++ b/snapcraft.yaml
@@ -40,7 +40,6 @@ parts:
             - mako
             - unidecode
             - lxml
-            - Yapsy
             - PyRSS2Gen
             - blinker
             - setuptools
diff --git a/tests/data/plugin_manager/broken.plugin b/tests/data/plugin_manager/broken.plugin
new file mode 100644
index 0000000000..1a5f9e05ce
--- /dev/null
+++ b/tests/data/plugin_manager/broken.plugin
@@ -0,0 +1,12 @@
+[Core]
+name = broken
+module = broken
+
+[Documentation]
+author = Chris Warrick
+version = 1.0
+website = https://getnikola.com/
+description = Broken (wrong category)
+
+[Nikola]
+PluginCategory = Task
diff --git a/tests/data/plugin_manager/broken.py b/tests/data/plugin_manager/broken.py
new file mode 100644
index 0000000000..68af857cb5
--- /dev/null
+++ b/tests/data/plugin_manager/broken.py
@@ -0,0 +1,42 @@
+# -*- coding: utf-8 -*-
+
+# Copyright © 2012-2024 Chris Warrick and others.
+
+# Permission is hereby granted, free of charge, to any
+# person obtaining a copy of this software and associated
+# documentation files (the "Software"), to deal in the
+# Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the
+# Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice
+# shall be included in all copies or substantial portions of
+# the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+"""The second plugin."""
+
+from nikola.plugin_categories import TemplateSystem
+
+
+class BrokenPlugin(TemplateSystem):
+    """The TemplateSystem plugin whose .plugin file says it’s a Task plugin."""
+
+    name = "broken"
+    broken_site_set = False
+
+    def set_site(self, site):
+        super().set_site(site)
+        print("Site for broken was set")
+        self.broken_site_set = True
+        raise Exception("Site for broken was set")
diff --git a/tests/data/plugin_manager/first.plugin b/tests/data/plugin_manager/first.plugin
new file mode 100644
index 0000000000..cae4442025
--- /dev/null
+++ b/tests/data/plugin_manager/first.plugin
@@ -0,0 +1,13 @@
+[Core]
+name = first
+module = one
+
+[Documentation]
+author = Chris Warrick
+version = 1.0
+website = https://getnikola.com/
+description = Do one thing
+
+[Nikola]
+PluginCategory = Command
+compiler = foo
diff --git a/tests/data/plugin_manager/one.py b/tests/data/plugin_manager/one.py
new file mode 100644
index 0000000000..817bd0770c
--- /dev/null
+++ b/tests/data/plugin_manager/one.py
@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+
+# Copyright © 2012-2024 Chris Warrick and others.
+
+# Permission is hereby granted, free of charge, to any
+# person obtaining a copy of this software and associated
+# documentation files (the "Software"), to deal in the
+# Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the
+# Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice
+# shall be included in all copies or substantial portions of
+# the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+"""The first command."""
+
+from nikola.plugin_categories import Command
+
+
+class CommandOne(Command):
+    """The first command."""
+
+    name = "one"
+    doc_purpose = "do one thing"
+    doc_description = "Do a thing."
+    one_site_set = False
+
+    def set_site(self, site):
+        super().set_site(site)
+        print("Site for 1 was set")
+        self.one_site_set = True
+
+    def _execute(self, options, args):
+        """Run the command."""
+        print("Hello world!")
diff --git a/tests/data/plugin_manager/second/second.plugin b/tests/data/plugin_manager/second/second.plugin
new file mode 100644
index 0000000000..ad1e4b8caa
--- /dev/null
+++ b/tests/data/plugin_manager/second/second.plugin
@@ -0,0 +1,13 @@
+[Core]
+name = 2nd
+module = two
+
+[Documentation]
+author = Chris Warrick
+version = 1.0
+website = https://getnikola.com/
+description = Do another thing
+
+[Nikola]
+PluginCategory = ConfigPlugin
+
diff --git a/tests/data/plugin_manager/second/two/__init__.py b/tests/data/plugin_manager/second/two/__init__.py
new file mode 100644
index 0000000000..14794c07ec
--- /dev/null
+++ b/tests/data/plugin_manager/second/two/__init__.py
@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+
+# Copyright © 2012-2024 Chris Warrick and others.
+
+# Permission is hereby granted, free of charge, to any
+# person obtaining a copy of this software and associated
+# documentation files (the "Software"), to deal in the
+# Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the
+# Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice
+# shall be included in all copies or substantial portions of
+# the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+"""The second plugin."""
+
+from nikola.plugin_categories import ConfigPlugin
+
+
+class TwoConfigPlugin(ConfigPlugin):
+    """The second plugin."""
+
+    name = "2nd"
+    two_site_set = False
+
+    def set_site(self, site):
+        super().set_site(site)
+        print("Site for 2 was set")
+        self.two_site_set = True
diff --git a/tests/helper.py b/tests/helper.py
index a39ad88f70..8fbebdb45b 100644
--- a/tests/helper.py
+++ b/tests/helper.py
@@ -6,23 +6,12 @@
 """
 
 import os
+import pathlib
 from contextlib import contextmanager
 
-from yapsy.PluginManager import PluginManager
-
-import nikola.utils
 import nikola.shortcodes
-from nikola.plugin_categories import (
-    Command,
-    Task,
-    LateTask,
-    TemplateSystem,
-    PageCompiler,
-    TaskMultiplier,
-    CompilerExtension,
-    MarkdownExtension,
-    RestExtension,
-)
+import nikola.utils
+from nikola.plugin_manager import PluginManager
 
 __all__ = ["cd", "FakeSite"]
 
@@ -55,24 +44,11 @@ def __init__(self):
             "TRANSLATIONS": {"en": ""},
         }
         self.EXTRA_PLUGINS = self.config["EXTRA_PLUGINS"]
-        self.plugin_manager = PluginManager(
-            categories_filter={
-                "Command": Command,
-                "Task": Task,
-                "LateTask": LateTask,
-                "TemplateSystem": TemplateSystem,
-                "PageCompiler": PageCompiler,
-                "TaskMultiplier": TaskMultiplier,
-                "CompilerExtension": CompilerExtension,
-                "MarkdownExtension": MarkdownExtension,
-                "RestExtension": RestExtension,
-            }
-        )
+        places = [pathlib.Path(nikola.utils.__file__).parent / "plugins"]
+        self.plugin_manager = PluginManager(plugin_places=places)
         self.shortcode_registry = {}
-        self.plugin_manager.setPluginInfoExtension("plugin")
-        places = [os.path.join(os.path.dirname(nikola.utils.__file__), "plugins")]
-        self.plugin_manager.setPluginPlaces(places)
-        self.plugin_manager.collectPlugins()
+        candidates = self.plugin_manager.locate_plugins()
+        self.plugin_manager.load_plugins(candidates)
         self.compiler_extensions = self._activate_plugins_of_category(
             "CompilerExtension"
         )
@@ -88,13 +64,9 @@ def _activate_plugins_of_category(self, category):
         """Activate all the plugins of a given category and return them."""
         # this code duplicated in nikola/nikola.py
         plugins = []
-        for plugin_info in self.plugin_manager.getPluginsOfCategory(category):
-            if plugin_info.name in self.config.get("DISABLED_PLUGINS"):
-                self.plugin_manager.removePluginFromCategory(plugin_info, category)
-            else:
-                self.plugin_manager.activatePluginByName(plugin_info.name)
-                plugin_info.plugin_object.set_site(self)
-                plugins.append(plugin_info)
+        for plugin_info in self.plugin_manager.get_plugins_of_category(category):
+            plugin_info.plugin_object.set_site(self)
+            plugins.append(plugin_info)
         return plugins
 
     def render_template(self, name, _, context):
diff --git a/tests/test_plugin_manager.py b/tests/test_plugin_manager.py
new file mode 100644
index 0000000000..8deb7a60b6
--- /dev/null
+++ b/tests/test_plugin_manager.py
@@ -0,0 +1,142 @@
+# -*- coding: utf-8 -*-
+
+# Copyright © 2012-2024 Chris Warrick and others.
+
+# Permission is hereby granted, free of charge, to any
+# person obtaining a copy of this software and associated
+# documentation files (the "Software"), to deal in the
+# Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the
+# Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice
+# shall be included in all copies or substantial portions of
+# the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+import nikola.plugin_manager
+
+from .helper import FakeSite
+from nikola.plugin_manager import PluginManager
+from pathlib import Path
+
+
+def test_locate_plugins_finds_core_plugins():
+    """Ensure that locate_plugins can find some core plugins."""
+    places = [Path(nikola.plugin_manager.__file__).parent / "plugins"]
+    plugin_manager = PluginManager(places)
+    candidates = plugin_manager.locate_plugins()
+    plugin_names = [p.name for p in candidates]
+    assert plugin_manager.candidates == candidates
+
+    assert "emoji" in plugin_names
+    assert "copy_assets" in plugin_names
+    assert "scan_posts" in plugin_names
+
+    template_plugins = [p for p in candidates if p.category == "TemplateSystem"]
+    template_plugins.sort(key=lambda p: p.name)
+    assert len(template_plugins) == 2
+    assert template_plugins[0].name == "jinja"
+    assert template_plugins[1].name == "mako"
+
+
+def test_locate_plugins_finds_core_and_custom_plugins():
+    """Ensure that locate_plugins can find some custom plugins."""
+    places = [
+        Path(nikola.plugin_manager.__file__).parent / "plugins",
+        Path(__file__).parent / "data" / "plugin_manager",
+    ]
+    plugin_manager = PluginManager(places)
+    candidates = plugin_manager.locate_plugins()
+    plugin_names = [p.name for p in candidates]
+    assert plugin_manager.candidates == candidates
+
+    assert "emoji" in plugin_names
+    assert "copy_assets" in plugin_names
+    assert "scan_posts" in plugin_names
+
+    assert "first" in plugin_names
+    assert "2nd" in plugin_names
+
+    first_plugin = next(p for p in candidates if p.name == "first")
+    second_plugin = next(p for p in candidates if p.name == "2nd")
+
+    assert first_plugin.category == "Command"
+    assert first_plugin.compiler == "foo"
+    assert first_plugin.source_dir == places[1]
+
+    assert second_plugin.category == "ConfigPlugin"
+    assert second_plugin.compiler is None
+    assert second_plugin.source_dir == places[1] / "second"
+
+
+def test_load_plugins():
+    """Ensure that locate_plugins can load some core and custom plugins."""
+    places = [
+        Path(nikola.plugin_manager.__file__).parent / "plugins",
+        Path(__file__).parent / "data" / "plugin_manager",
+    ]
+    plugin_manager = PluginManager(places)
+    candidates = plugin_manager.locate_plugins()
+    plugins_to_load = [p for p in candidates if p.name in {"first", "2nd", "emoji"}]
+
+    plugin_manager.load_plugins(plugins_to_load)
+
+    assert len(plugin_manager.plugins) == 3
+    assert plugin_manager._plugins_by_category["ShortcodePlugin"][0].name == "emoji"
+    assert plugin_manager._plugins_by_category["Command"][0].name == "first"
+    assert plugin_manager._plugins_by_category["ConfigPlugin"][0].name == "2nd"
+
+    site = FakeSite()
+    for plugin in plugin_manager.plugins:
+        plugin.plugin_object.set_site(site)
+
+    assert "emoji" in site.shortcode_registry
+    assert plugin_manager.get_plugin_by_name("first", "Command").plugin_object.one_site_set
+    assert plugin_manager.get_plugin_by_name("2nd").plugin_object.two_site_set
+    assert plugin_manager.get_plugin_by_name("2nd", "Command") is None
+
+
+def test_load_plugins_twice():
+    """Ensure that extra plugins can be added."""
+    places = [
+        Path(nikola.plugin_manager.__file__).parent / "plugins",
+        Path(__file__).parent / "data" / "plugin_manager",
+    ]
+    plugin_manager = PluginManager(places)
+    candidates = plugin_manager.locate_plugins()
+    plugins_to_load_first = [p for p in candidates if p.name in {"first", "emoji"}]
+    plugins_to_load_second = [p for p in candidates if p.name in {"2nd"}]
+
+    plugin_manager.load_plugins(plugins_to_load_first)
+    assert len(plugin_manager.plugins) == 2
+    plugin_manager.load_plugins(plugins_to_load_second)
+    assert len(plugin_manager.plugins) == 3
+
+
+def test_load_plugins_skip_mismatching_category(caplog):
+    """If a plugin specifies a different category than it actually implements, refuse to load it."""
+    places = [
+        Path(__file__).parent / "data" / "plugin_manager",
+    ]
+    plugin_manager = PluginManager(places)
+    candidates = plugin_manager.locate_plugins()
+    plugins_to_load = [p for p in candidates if p.name in {"broken"}]
+    plugin_to_load = plugins_to_load[0]
+    assert len(plugins_to_load) == 1
+
+    plugin_manager.load_plugins(plugins_to_load)
+
+    py_file = plugin_to_load.source_dir / "broken.py"
+    assert f"{plugin_to_load.plugin_id} ({py_file}) has category '{plugin_to_load.category}' in the .plugin file, but the implementation class <class 'tests.data.plugin_manager.broken.BrokenPlugin'> does not inherit from this category - plugin will not be loaded" in caplog.text
+    assert len(plugin_manager.plugins) == 0
diff --git a/tests/test_template_shortcodes.py b/tests/test_template_shortcodes.py
index c6c948da97..148f7e6091 100644
--- a/tests/test_template_shortcodes.py
+++ b/tests/test_template_shortcodes.py
@@ -67,7 +67,7 @@ class ShortcodeFakeSite(Nikola):
     def _get_template_system(self):
         if self._template_system is None:
             # Load template plugin
-            self._template_system = self.plugin_manager.getPluginByName(
+            self._template_system = self.plugin_manager.get_plugin_by_name(
                 "jinja", "TemplateSystem"
             ).plugin_object
             self._template_system.set_directories(".", "cache")