Joomla 4 is published already and
JEvents is ready for it for some time now:
Read the blog about the J4 compatibility of the main component:
https://www.jevents.net/blog/jevents-3-6-exciting-new-styling-featured
I have not checked, if this is true for all plugins, but you can check it in the version history/ change log of each plugin you are interested in. You find it on the download page of each plugin. - Or maybe Tony can give a general information. This might be an interesting point for the FAQ section of the homepage.
The (silver) custom fields plugin e.g. is J4 ready from 3.6.2 onwards
https://www.jevents.net/download-area/silver-downloads/467-jevents-custom-fields
The (bronze) meta tag plugin is J4 ready from 3.6.0 onwards
https://www.jevents.net/download-area/bronze-downloads/447-jevents-meta-tags