Another tactic that developers now use is to have a fully functional app in the first-downloaded instance, but then the application slowly degrades as updates occur to encourage an up-sell. As a dev myself, I've directly seen this happen with apps I cannot specifically shame online.
I'm primarily referring to mobile apps. I have an SD card with my music library on it. The choice of apps there gets more complex... As phone makers remove SD card functionality, and headphone jacks, and limit out of the box music players, the ability to use my phone for music is also fading. I have had apps corrupt my locally saved music library as well in attempts to force me into buying streaming services perhaps, I no longer trust many services in app stores.
trayplayer.com
As for mobile audio I use Spotify but I have a library of mp3s on my SD card that I play with the default Samsung Music app which works just fine. No ads in that so far. If you haven't tried a modern BT 5.0 device, try giving bluetooth another chance.
I have 30Go of music files on my laptop, that I carefull update, and backup. I add to the collection once in a while.
But few do that anymore: no cd player in devices, and file systems are being abstracted away remember?
So they listen to music on youtube, spotify, soundcloud, etc.
They don't own the music, hence they can't chose the player.
You simply can't trust free apps any more. Probably can't even trust many of the paid ones because making people buy the same thing multiple times is more profitable for opportunistic individuals.
Keep backups in multiple (independent) locations.
But FOSS apps are still there for you.
VLC is to this day the best video players, across all OS, and can read music.
It's as not convenient to play music though.
re:parent comment, i feel like the streaming "free" music app/services are more iterations on radio stations rather than iterations on music players since radio has ads, pseudo random playlists, requirement to be "connected" etc.
Maybe unpopular opinion, but in comparison w/radio, I tend to think streaming actually looks pretty good.