zank In the folder /media/SHARE/system you find a file named “costum-es-config”. Open it with the editor and insert the line in “COSTUMISATIONS” like:
#####################
## CUSTOMISATIONS ###
# to customize your display, you can create the file /userdata/system/custom-es-config
# including this kind of commands
# rotate the screen
# xrandr -o left
# xrandr -o right
# xrandr -o inverted
# change the resolution
# xrandr -s 640x480
xrandr --output HDMI-1 --mode 1280x720 --rate 60 --primary --set underscan on --set "underscan hborder" 20 --set "underscan vborder" 4
# change the resolution and the Hz
# xrandr -s 640x480 -r 60
#####################
After this, copy the file in /userdata/system
Finish!
PS: It is only on HDMI 1 on RPi4 (you can change, if you want)