I was having the same issue. It seems that the branch 12 days ago is to blame and any builds after that point have the same issue. If you uninstall and manually install the apk from 18 days ago it, you should get working folders again.
The devs have the apks posted here (this link should take you straight to the last build where folders were working) : Plex for Android - #465 by marekszulik
In case it helps with troubleshooting if someone at plex can investigate:
Folder view on Android 9.20.1 looks like this and works as expected: Plex Android 9.20.1 Folder - Album on Imgur
Folder view starting on Android 9.21.0 looks like this and prevents you from clicking further into sub folders: Plex Android 9.21.0 Folder View - Album on Imgur
In both cases, you can click and hold to view sub options (Play Folder, Shuffle, etc) so they can technically be interacted with, but starting in 9.21.0 you can no longer tap to enter sub folders.
For now, I’m going back to 9.20.1 but let me know if I can provide any additional info that might help resolve it.
Hope this helps OP and Plex staff!
