The last 3 years I've been very happy with "YouTube Vanced", in particular because of: background play, native adblocking, fully native logged in experience if desired, AND it switches to audio only encode if background play is enabled so it saves data.
NewPipe also has background play that only uses the audio feed. I thought I would miss the logged in experience but if you take a few minutes to subscribe through the app, the UX is actually better or at least on par with the native youtube app.
The last 3 years I've been very happy with "YouTube Vanced", in particular because of: background play, native adblocking, fully native logged in experience if desired, AND it switches to audio only encode if background play is enabled so it saves data.
Get it here: https://vanced.app/