[my123]

Going to answer point by point:

> That said, we know at least the VMkernel is likely to work on other ARMs, though userspace might not like it if you don't have things like AMX in your CPU, or the SPRR stuff

Open-source XNU doesn't support Apple's CPU extensions, but macOS still runs just fine on it. (but no Rosetta of course)

> by passing through Metal, as I understand it

See ParavirtualizedGraphics.framework, which uses MetalSerializer.framework under the hood.