I'm not the person you asked, and I don't care if you buy YT premium, but Firefox mobile can play background videos, the only finicky thing is it pauses when you turn your screen off, but you can press play on your lockscreen to start it again.

I use smarttube next on my television.

For music, I personally do Qobuz because they pay marginally better than Spotify (albeit still not a ton.)

If you remove a snail's shell, you'd think they'd be faster because of the reduced weight. However, they actually become slower.

That's because when you remove their shell, they become a bit more slug-ish!