This video is kind of a fail, and it's super dark even though I turned the gamma correction way up. Also music is pretty loud, be warned! I keep forgetting to turn it down :/// Sorry, my friends.
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