Did this question ever get answered? I'm facing a similar issue. Have already purchased 2 different higher end Nvidia GPUs 8 & 11GBs that worked great for all other apps but required Nvidia drivers to work on my Mac Pro 5,1 10.12.6. Opening Painter immediately crashes the system. So I want to know: What GPU options are there for Mac users? System Requirements (and experience) says must use Apple default drivers, at least 2GB VRAM (preferably 4+), CUDA necessary for IRay (implying NVIDIA). I can't figure out what card this could be that is Nvidia (CUDA), ≥4GBs VRAM, able to run on Apple default drivers. Anybody have ideas?
Mac Pro 5,1
2 x 3.33 GHz 6-Core
10.12.6
64GB RAM
currently GTX 760 2GB