Here are some of the Joomla Extensions we have encountered that are never going to have a working Joomla 4 version.

Ajax Intro Articles Module

"Ajax Intro Articles Module" is not available for Joomla 4. This module presents an alternative layout for displaying Joomla articles in a blog layout. 

You do not need an extra extension for an article blog layout view in Joomla 4 as it is included as a menu item type in the core.

However, for simplicity we recommend these alternatives to our clients who use our Monthly Joomla Management Package: