Armbian - need help, locked out myself by setting backlight to zero

[guidol]

The fix is to either login via serial/network and tweak the right sysfs path

for network - when armbian is normally iinstalled - it uses the network-manager.
so when you then insert a USB-Ethernet-Dongle this would use DHCP and you can connect via ssh.
Then you have to find/edit the screen setting.
Network access on the Pinebook would be much more easy than a serial-port-login , because a usb-serial-donge would automatically become a serial-terminal