can you upload a screen shot of your display preferences window? Also the graphics/display in “about this mac” system report. Maybe a quicktime screen recording of hitting function buttons? Screen brightness, volume, keyboard brightness, etc
Also, have you done a full safe boot? The safe boot definitely clears out some errant AMD caches and whatnot.
It seems odd that it would be kext related, when really how it works is just simple DDC messages to the backlight controller. So it should be related to the function key kexts, rather than the GPU kexts. I don’t doubt that Apple over complicated something, but it seems entirely unnecessary.
Have you messed with KEXTS at this point on this MBP? I ask because all the ones I’ve done with the r8911 method, i did nothing at all with KEXTS.
Nothing else at all
I don’t have one here to test functionality at the moment, but i would be so surprised if i sent them out with brightness and sleep non functional and no one complained.