Comment 8 for bug 1829641

Alf, the backlight CAN be adjusted with the dialog box, but not using the keys (which call lxqt-config-brightness). I can verify this by adjusting it then catting /sys/class/backlight/amdgpu_bl0/brightness :

Max
cat /sys/class/backlight/amdgpu_bl0/brightness
255

Min
cat /sys/class/backlight/amdgpu_bl0/brightness
13

I did chmod a+w on /sys/class/backlight/amdgpu_bl0/brightness to make absolutely sure it is accessible in case that is the issue, but it made no difference. lxqt-config-brightness -d and lxqt-config-brightness -i still adjust the brightness/gamma rather than the backlight.

Walter, I tried lxqt-backlight_backend --inc as in your link, but it does not work (as above, even after having changed the permissions on the /sys/class/backlight/amdgpu_bl0/brightness file:

retro@howard:~$ cat /sys/class/backlight/amdgpu_bl0/brightness
13
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ lxqt-backlight_backend --inc
retro@howard:~$ cat /sys/class/backlight/amdgpu_bl0/brightness
13

Also as per comment #2, lxqt-config-brightness -r still returns "Debug: No outputs have backlight property"