I tried to adjust the screen brightness using both the command line and xfce system setting, the screen only flashed for a brief second, but the brightness didn’t change at all, the command line I was using is
I cannot duplicate the problem, on an up-to-date A-06: xbacklight reports that No outputs have backlight property, but entering a value into /sys/class/backlight/backlight@0/brightness correctly changes the brightness.
The default value was 5, so I tried 9 and 2 - which correctly made the display brighter and darker respectively.