pi@openplotter:~ $ xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 7680 x 7680
HDMI-1 connected primary 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768      60.00* 
   800x600       60.32    56.25  
   848x480       60.00  
   640x480       59.94  

pi@openplotter:~ $ xrandr --output HDMI-1 --rotate inverted

** flip **

pi@openplotter:~ $ xrandr --output HDMI-1 --rotate normal

** flop **

pi@openplotter:~ $ cat /usr/share/dispsetup.sh 
#!/bin/sh
if ! grep -q 'Raspberry Pi' /proc/device-tree/model || (grep -q okay /proc/device-tree/soc/v3d@7ec00000/status 2> /dev/null || grep -q okay /proc/device-tree/soc/firmwarekms@7e600000/status 2> /dev/null || grep -q okay /proc/device-tree/v3dbus/v3d@7ec04000/status 2> /dev/null) ; then
if xrandr --output HDMI-1 --primary --mode 1024x768 --rate 60.00 --pos 0x0 --rotate normal --dryrun ; then 
xrandr --output HDMI-1 --primary --mode 1024x768 --rate 60.00 --pos 0x0 --rotate normal
fi
fi
if [ -e /usr/share/tssetup.sh ] ; then
. /usr/share/tssetup.sh
fi
exit 0

pi@openplotter:~ $ # Zo pas je die file aan, maar als het verknooit zit je met de gebakken peren:

pi@openplotter:~ $ sudo nano /usr/share/dispsetup.sh