Let's be honest, the first time we tried this it didn't go so well. This time however, I think your facemask is going to go on just fine. Why do you need a facemask? That's not important, what is, is that your relaxed. So relax damn 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