You come across a strange little shop late one night, out of curiosity you decide to pop in to take a look around. Perhaps you might even find something useful. Still learning the whole 'sound effect' thing and whatnot. At least I only tripped over my words once while trying to keep my dog quite xD
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