I can't say this was a pleasant sensation, but it has been a requested video, so thought I'd give it a try. I wont be doing old fruit again in a hurry. Worth a share just so you can view it. Someone might like it!
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