[londons_explore]

You don't have to emulate the hardware directly. Since apples kernel is opensource, there's a good chance one could write a kernel driver for another GPU offering a sufficiently compatible interface. Nearly all GPU code will have software rendering fallbacks too, so the driver might just be enough to trigger those fallbacks.

[Wowfunhappy]

Has anyone ever successfully written a custom GPU driver for macOS? Perhaps there would be more incentive to do so now, but... seems like a pretty massive undertaking.

You could of course use the software renderer—I'd guess that probably still exists on Apple Silicon Macs for safe mode and such—but it wouldn't be pleasant...

Edit: Well, anyone besides nVidia, I suppose. But they're a big company, not a Hackintosh side project.

[floatboth]

At least with the previous versions of macOS you didn't have to do anything special, the software renderer would just work if you don't have a supported GPU.

[my123]

And that doesn't change in Big Sur.