Life's been so crazy, I haven't been able to post in a while. Thank you so much for your patience and support, and you can expect more regular posting from now on! Love ya'll!
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