Can't stop, won't stop, don't even know how to stop. I apologize for: 1) my cats 2) the quality 3) the noisy street I live on -_-; I recommend headphones :)
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