So I think I may have stumbled upon a way to use the full potential of YouTube music for free on any device utilizing the Firefox browser. Well, maybe not every device since Firefox can't be used on every device. I know for sure this will work on Android.

1) download the Firefox browser on your device

2) go into the add-ons section in firefox and install 2 add-ons. (Video background play fix, and ublock origin)

3) now search for m.youtube.com and type in a band of your choice. When you choose the album playlist to play it should allow you turn off the screen and play in the background.

There you have it. Free "somewhat legal I guess" YouTube music. In my experience so far there have been no ads and the music does play but it might require you to tap the screen on wake and press play. This process is buggy for sure, but you can't really beat free. Hope this helps someone.