Hey guys, I'm chiming in here: I was about to start a thread on this very topic, and this one popped up as already existing. Has anyone been able to find an answer to this? The last post here was from Dec, 2021, and now it's almost Feb, 2022, I have the latest version of the YouTube app on iOS 15.3, iPhone 12 Pro Max, and it's still gone, with only the manual Dark mode toggle. Like others here, I had it setup and working and then all of a sudden it was gone. To make sure it wasn't on my end, I removed the app on my iPad, rebooted and reinstalled the app as a test, and it didn't come back. This means it's probably not on my end, and I don't need to repeat this on the phone (unless someone has some info on this.)
Thanks