I'm using VMware, I'm not sure if that uses KVM. It should have GPU passthrough though, yes.
Mind, VMWare + GPU passthrough really should have more than acceptable performance, so I'm surprised.
Do you know a type-1 hypervisor I could use on Linux? Will QEMU do? Thanks for the info!
It's a somewhat involved process, especially for GPU passthrough.
But on Linux, you can do GPU passthrough on Linux for macOS (and Windows) guests.
In particular, since no VM has graphics acceleration for macOS guests, and because macOS relies very heavily on graphics acceleration, GPU passthrough is basically the only way to comfortably use macOS inside of a VM.