For brightness control, there is a lightweight tool called brightnessctl, which is available in the community repo. If you are using i3wm, you simply have to add two keybindings that call brightnessctl. For example:
bindsym XF86MonBrightnessUp exec --no-startup-id brightnessctl -q set +5%
bindsym XF86MonBrightnessDown exec --no-startup-id brightnessctl -q 5%-
I wasn’t aware you have to mess around with X Server configuration files to enable backlight…