I apologise that i didn't do a longer video than this. When i was recording this video i thought the noise of people outside would be picked up into my audio recorder but i think watching it back, i don't think you can hear it as such.
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