It's a Fairphone F3 on Android 10.
The problem was the gesture setting like you suggested, but it was the opposite: I was using 2-button navigation, tried switching to Gesture navigation and now everything is fine!
Also noticed there is now an x at the top centre of the screen to exit, it wasn't there before, even in portrait mode. I had to exit without it .... Try, you'll see what a pain it is
Love you Mike