Add build description for Qt6, marked as hidden

content/getting-started/download-and-install/build-instructions-ubuntu-qt6.md

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+title = "Build Instructions Ubuntu Qt6 - Basic"
+published = true
+hidden = true
+weight = 30
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+
+## Dependencies and Prerequisites
+
+This page is mainly build instructions for Ubuntu, but some comments are also added for RHEL8 and Windows. 
+
+Basic instructions without Python binding and GRPC.
+
+
+### Configuration and build
+
+| Tool                    | Minimum version  | 
+|-------------------------|------------------|
+| gcc                     | 11               | 
+| python 				  | 3.8              | 
+| Qt 	    			  | 6.5              | 
+
+
+Update apt installer
+
+    sudo apt update
+
+Install GCC and related tools
+
+    sudo apt install build-essential curl zip unzip tar flex bison
+
+[Set default compiler](https://linuxconfig.org/how-to-switch-between-multiple-gcc-and-g-compiler-versions-on-ubuntu-20-04-lts-focal-fossa)
+
+Dependencies for RHEL8
+
+    yum install curl zip unzip tar flex bison perl-IPC-Cmd gcc-toolset-10 freeglut
+
+### Clone and update sub modules
+
+	git clone https://github.com/OPM/ResInsight
+    cd ResInsight
+    git submodule update --init
+
+### Build and install required dependencies using vcpkg
+vcpkg is located in the folder ThirdParty/vcpkg. The packages to be installed is specified in vcpkg.json. The actual install of the selected packages are done in the CMake configure step.
+
+    ThirdParty/vcpkg/bootstrap-vcpkg.sh
+
+### (Windows) Build and install required dependencies using vcpkg 
+Open a command prompt using "Run as Administrator" for Visual Studio x64.
+
+[Detailed Developer notes](https://ceetronsolutions.github.io/resinsight-system-doc/editor/vcpkg)
+
+    ThirdParty/vcpkg/bootstrap-vcpkg.bat
+
+### Qt
+
+The version of Qt  ResInsight depends on is probably not available as a package for the Linux distribution you are working with. Here is a short description on how to install a custom Qt version.
+
+[aqtinstall](https://github.com/miurahr/aqtinstall) is a Python tool used to install precompiled versions of Qt. Other ways to install Qt is described [official Qt documentation](https://www.qt.io/download-qt-installer-oss)
+
+
+Create a root folder for Qt installations. In this folder, create a virtual environment for **aqtinstall**:
+
+    python3 -m venv myvenv
+    source myvenv/bin/activate
+    pip3 install aqtinstall
+    aqt install-qt linux desktop 6.6.3 -m qtcharts qt5compat qtnetworkauth
+
+
+### Build ResInsight
+
+Install Ninja build tool
+
+    sudo apt-get install ninja-build
+
+The configuration flags for a basic build is given in `CMakePresets.json` in the root of the repository. Configuration flags specific for the system to build on can be specified in `CMakeUserPresets.json`. This file is ignored by git.
+
+- Create a copy of `CMakeUserPresets-example.json` and rename to `CMakeUserPresets.json`
+- Update the path to your local installation of Qt6 for the key `CMAKE_PREFIX_PATH` in `CMakeUserPresets.json`
+
+Set current working folder to the root folder of the ResInsight repository. Execute the following commands to build ResInsight:
+
+    cmake . --preset=linux-base
+    cd build
+    ninja
+