My F5 and F6 keys don’t work in lubuntu.
They are interpreted directly by the keyboard (I’m not sure what, something to do with the RGB).
The fn+f5 or fn+f6 are XF86KbdBrightnessDown and Up and shown by ScreenKey.
I did the:
options hid_apple fnmode=2 swap_opt_cmd=1 (modprobe options)
and that works for all the other function keys.
This keyboard is really bad for Linux. 