It seems that rock5b does not support 1920x1200 resolution.
1920x1200 resolution not supported
Android or Linux?
rock-5b-debian-bullseye-xfce4-arm64-20220924-1313-gpt.img.xz
Is Rock 5B meanwhile supporting 1920x1200 resolution with Linux? If yes - how can I activate it?
Workaround found:
The problem was that screen content was distorted. This makes round shapes appear elliptical.
As a workaround I have now transformed the desktop with xrandr. That works fine. The resolution remains the same, but the content is no longer distorted, even though the entire screen area of the monitor is used.
xrandr --output HDMI-1 --transform 1.0,0,0,0,1.1,0,0,0,1 |xrandr --output HDMI-2 --transform 1.0,0,0,0,1.1,0,0,0,1