No video AirPlay from app, only with "Duplicate Screen"

I have tried to AirPlay various videos, h.264 and HEVC from my iPhone XR with iOS 14.2 to my Apple TV 4K and my new LG CX (which supports AirPlay 2). When airplaying from the iPhone app I get either the audio with the TV show’s poster or nothing at all. On either device (ATV or LG).

It works with subtitles and all duplicating the screen, but the compression isn’t quite good and it is also my understanding that it would consume quite some battery.

I am puzzled because I am quite sure it worked from my iPhone to the ATV with iOS/tvOS releases 13.x.

Am I doing something wrong, is there a particular setting or it’s broken? I was planning to move the ATV in the living room together with my older Android Bravia!!