If you're on android then NewPipe is fantastic for watching YouTube without adverts, in a hovering window or even just listening to the audio with the screen of

If you're on android then NewPipe is fantastic for watching YouTube without adverts, in a hovering window or even just listening to the audio with the screen off. It does not tie into your YouTube account (so no watch history or recommended vids) which may or may not work for you, but it's a fantastic resource.