Somehow I found out that full screen can be entered when swiping up from the bottom of the screen using two fingers.

It then shows a tiny popup, telling to do it downwards from the top of the screen to exit.
That does not work. Instead some player controls appear.
So the popup message is misdirecting (wrong).

I managed to find out that repeating the first mentioned gesture exits full screen.

If any of this is mentioned in the manual, it is well hidden.

Hi, Heliman. What is the model of your device? What is the version of your app? Thanks for your support.

iphone se with dji go 4.1.20