I used Plex for my home media for almost a year, then it stopped playing nice for reasons I gave up on diagnosing. While looking at alternatives, I found Jellyfin which is much more responsive, IMO, and the UI is much nicer as well.
It gets relegated to playing Fraggle Rock and Bluey on repeat for my kiddo these days, but I am absolutely in love with the software.
What are some other FOSS gems that are a better experience UX/UI-wise than their proprietary counterparts?
EDIT: Autocorrect turned something into "smaller" instead of what I meant it to be when I wrote this post, and I can't remember what I meant for it to say so it got axed instead.
To that I'd add Simple Gallery and some of the other "Simple" apps by the same dev, Tibor Kaputa.
Honestly, F-Droid should be your first stop on Android because the open source apps are usually better. Most apps on the play store are basically just adware at this point.