New Plex client update on my APPLE TV 4 does not work anymore with my old Server QNAP TS-431

Fair point :wink:
You can bookmark the release announcement thread for Plex on Apple TV (using the forum “bookmark” function at the end of the thread). This way you will get an e-mail notification with some info what’s in each release (unless you disabled e-mail notifications).

Edit: modified version of the link to the release announcements of Plex for Apple TV