I have a MacBook Pro (Retina, Mid 2012) with a non-functioning NVIDIA dGPU, which I've disabled using the NVRAM method . On MacOS Sierra, 10.12, this method (and moving the NVD* kexts) worked perfectly, including sleep/wake and brightness.
Unfortunately I needed to update to MacOS Catalina, 10.15, for some required software compatibility, and now when it wakes from sleep, the display remains off (either it's trying to use the dGPU or the backlight does not come back on); brightness keys also no longer work. I can ssh in, so it's clearly waking from sleep, just no display, and I have to reboot. It's the same whether I use the software menu or close to laptop lid to sleep. Interestingly, the display sleep (set to a 10 minute timer in System Preferences) works fine (the backlight comes back on afterwards).
Maybe is there a specific new kext that can be unloaded, and the equivalent kext from sierra loaded in its place? Otherwise, are there any low-level direct controls for the backlight?
sudo pmset -a gpuswitch 0 and
sudo kextload /NVIDIA_BAK/NVDAResman.kext after login, but to no avail.
I'm aware of some hardware fixes  and  but I'm not sure if they apply to my specific model with NVIDIA dGPU, as this issue seems to be slightly more common with the previous AMD dGPU model. Ideally I'm hoping this can be fixed in software (and is revertable), as it clearly worked on sierra.