I found a KMart! Woo hoo! Come see what I found inside! I had hoped to do a walk-through in there to show you what it's like, but the music was waaay too loud. Maybe I can go back in the future and do one, then just record some audio later, I don't know. We'll see.
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