So I went out last weekend and someone ordered me a beer. The problem is they didn't say who it was from. Journey down the rabbit hole with me and let's see if we can solve this mystery together.
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