I was hoping this would solve the issue, but sadly it doesn't. I found that it can also be "solved" by setting the contentInset.top to some negative value. But that doesn't hold for all sizes of phones. It's weird because it happens only in iOS 15. I will have to try to investigate more or hope that it is just an early beta defect that will be fixed later.

I can confirm that it happens on projects created before as well.

Works like a charm, nice find! This worked for my case!

This answer has already been suggested in this thread and no, it does not remove the unwanted space. It might work for some cases but not mine.