What just worked for me, (on a laptop, not sure for desktop) is to mess with the settings in the BIOS that control the Fn key behavior. i.e. function keys work as function keys and secondary controls are while holding the fn key+F key. With this I can now control the brightness with fn+f4/f5. be warned not to spam it, because it will get stuck in the adjustment cycle, displaying the brightness bar in the GUI, if that makes sense.