Matthew GarrettHuh ok so doing UGA (the obsolete UEFI graphics spec that is not fully publicly documented) involves running a weird VM that is probably EFI Byte Code but not entirely clear, and Apple shipped a couple of generations of machines that implemented UGA and not GOP, did Apple actually ship a UGA implementation at anything other than the firmware layer?
p4block@mjg59 rumor says that Nvidia randomly added UGA support for their GPUs "recently" (may have been 1000 series, but I don't remember well)
GPUs that don't work on macOS at all magically show the boot prompt on the Mac Pro 5,1... For some reason.