This is not everything. For some reason my computer stopped recording like a good 20 minutes of my filming, but it was still showing that it was filming. So not sure what happened but I hope you enjoyed this video!
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