Hey there :) I'm gonna feel up your ears and there's nothing you can do about it. Haha just kidding you could always exit the video but why would you do that? :( Today I'll be touching the mics on my camera (my phone) which is basically like me giving you an ear massage.
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