As the title indicates, unless you actually start to play some media files (anything) the screen saver does not activate. This means that if you start Plex on your Samsung TV and walk away, hours later the screen will still be displaying the menu. If you simply click on any media and then stop and leave at menu, the configured screen saver will activate at the appropriate time-out.
I had originally posted about this issue months ago (thread now closed) but couldn’t see what was wrong until now.
https://forums.plex.tv/t/plex-client-on-samsung-tv-screen-saver-broken/836970