ext_tables.php

<?php
/**if (!defined('TYPO3_MODE')) {
	die ('Access denied.');
}

\TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin(
	'Ubl.Rssnews',
	'Rssnews',
	'RSS News Feed'
);
$extensionName = \TYPO3\CMS\Core\Utility\GeneralUtility::underscoredToUpperCamelCase($_EXTKEY);
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile($_EXTKEY, 'Configuration/TypoScript', 'RSS News Feed');

$pluginSignature = str_replace( '_', '', $_EXTKEY ).'_rssnews';
$GLOBALS['TCA']['tt_content']['types']['list']['subtypes_addlist'][$pluginSignature] = 'pi_flexform';
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPiFlexFormValue(
	$pluginSignature, 'FILE:EXT:' . $_EXTKEY . '/Configuration/FlexForms/flexform.xml'
);*/