Oh my goodness. I know. "Why is she in this aisle again?" I ask myself the same question sometimes, but something just keeps pulling me back there. I love it! The cavities! The crinkles!
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