Well ultimately its also just a russian nerd building a nice program, but I get where you’re coming from. Good luck with your search and hopefully you’ll find what you’re looking for.

I also felt that way first but ultimately resigned as I couldnt find a decent alternative. Just curious, are you concerned about spyware/potentially malicious updates or do you just want to be sure/free of proprietary software?

I use AIMP. My Library has roughly 6k files, it has replay gain and mostly when I add new files it notices it automatically and includes them in the library relatively quickly. You can also choose to manually scan for just tag or cover changes. And as a nice bonus, there are a few user made themes you can use to customize the look of the app. My only critique of the app up to date is, that the audio suffers a bit when using volume boost and that the ui requires a bit of learning how to use it.

On any Fedora based distro you can quite easily install the proprietary nvidia drivers (this is necessary for a good experience btw). For windows programs you could take a look at winboat, it basically spins up windows in docker and it doesnt need any configuration whatsoever. For an animated wallpaper, KDE Plasma has a wallpaper engine plugin. Its a bit fiddly as I remember and not every wallpaper works, but its good enough for me.