Sorry I haven't uploaded in a while! I got a few requests for scratching on the black table that I have in a lot of my videos, so here it is - a pure tapping video should be going up tomorrow too!
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app