All the other Fn + F1 thru F12 keys were working except for Fn + F5 & Fn + F6.
Open keyboard settings and find Application Shortcuts.
Add a new shortcut with the following command:
Reduce brightness by 10%:
I used the keyboard shortcode Alt + (-), meaning the minus key on my numpad.
Increase brightness by 10%:
I used the keyboard shortcode Alt + (+), meaning the plus key on my numpad.
My laptop keyboard has a number pad so this is pretty comfortable, but if you don’t have a numpad, you’ll need to choose a different unused combination.
WARNING: Don’t try and set the keyboard as Alt F4 and Alt F5 because are already bound to “close the window”…