NewPipe has a "background mode". There's a short hiccup when you switch to "background mode" but you can still control it from there so it's not so bad.
I find it shocking that Google is permitted to charge money for a feature like that, when as far as I can tell most of the music on Youtube was uploaded without permission of the copyright owner.
I mean, they're not, according to their own ToS (or even their own interpretation of it).
It says something in there along the lines of video and audio may not be separated. On the basis of which, they ran a witch hunt on all 3rd party YouTube apps on the Play Store, which had a background playback feature.
This in itself makes no sense, as separating video and audio during playback had always been possible on the desktop by simply switching to a different tab in your browser or minimizing the window.
But obviously, this wasn't about showing integrity. They published YouTube Red with its background playback feature just a few months after this witchhunt.
And since the Play Store is their property, they didn't even need a legitimate basis for throwing these apps out. They own the market, so they were able to just shut out the competition.