Leap 15.0 on MacBook Pro 17" A1297 2010 brightness adjustment not working

Hi

Anybody has a solution for adjusting brightness on the GMUX device on a MacBook Pro 17" ?

Machine:
MacBook Pro 17" A1297 from 2010 with Radeon Intel combo and GMUX device

Problem:
Brightness buttons are working but are adjusting the Intel brightness and not the GMUX brightness.

I can echo new values to the GMUX brightness (as root) and that works but I can’t get the brightness adjust buttons (Fn+F1 and Fn+F2) to change the GMUX valuses.

Regards
Maciej