I noticed that this afternoon. I was on YouTube for about an hour. I first noticed that the phone was warm. I’m going to keep an eye on YouTube. I’ve since updated to iOS 14.4.2. It’s fine now.
I was watching a video by Brandon Butch this afternoon and he mentioned that he’s pretty sure that the battery life was worse on 14.4.1. And that hopefully it will be better on 14.4.2.