I tried Jellyfin. Although it is great for an open source project, it lacks polish. Especially on the android TV app, there are multiple obvious problems. I encountered too dealbreakers within the first half hour of usage:

- Resume does not work reliably

- Subtitles are ugly and un-configurable

I will keep monitoring it from time-to-time, and switch from Plex as soon as these 2 problems are fixed. Thanks for recommending, I have been on the lookout for such an app for a long time.