Volumio x86 with 7 inch touch screen

Iam trying to setup Volumio x86 2.03 on a Gigabyte J1800N with the Rev 2.1 Waveshare 7 inch touch screen.

Volumio works pretty well connected to my TV with a common resolution 1920x1080 but it refuses to show anything on the Waveshare display with 1024x600.

On the other hand connecting the touch display to a Win10 install or default Raspbian on a raspberry with forcing the resolution works too
So the display seems to work properly

The command “xrandr” always drops the error “Can’t open display”. xrandr which so far I understand can add resolution modes (with cvt creating the right syntax).
Since I could not find an xorg.config I created one with the right resolution but this does not work either, also Iam not sure if x server is reading it. :wink:

Does any linux guru have any hint how I could force the resolution since I guess is the main problem.

thanks in advance Reinz