I have a MacBook Pro 10,1 mid 2012 and when I tried the live CD image (with the open source drivers), brightness control worked perfectly, but after I installed the OS (also open source drivers), I am not able to adjust the brightness, I tried on both KDE Wayland and Xorg.
@meky
I tested with Fn+F11/F12 in live EOS-Gemini - it does nothing.
yay -S brightnessctl
brightnessctl s 10%-
brightnessctl s 10%+ See how to assign to keys
or write two scripts as an example bridn.sh /briup.sh
#!/bin/bash
brightnessctl s 10%-
(chmod +x bridn.sh is needed) and assign to shortcuts