Airsonic Advanced and DSUB on Android are pretty good options since DSUB has advanced local caching options.
I aquire my music then run it through Picard for tagging which places it into my NAS where it is mounted to airsonic and jellyfin containers for consumption.
The jellyfin apps have gotten a lot better and I find myself using feishin and finamp more often lately.
I’ve found the opposite to be the case unfortunately. Plex “just works” while my jellyfin server had almost constant issues with subtitles (two of my frequent users need these because of hearing problems) and would frequently crash requiring docker restarts.
I adopted jellyfin very early, used it for many (maybe 6?) years and these problems only got worse over time.
I always prefer open source (often to a fault) but I am glad I switched to Plex a few months ago. I got the lifetime pass for cheap for black Friday. I still leave jellyfin running for a few users, but everyone else has already switched over.