Apple never released a driver that supports Vulkan out of the box, therefore MoltenVK was born, which translates Vulkan IR to Metal source then recompiles to Metal shaders.
replyThis was the pipeline in Proton for macOS (I'm not sure if it's still is the case, been quite a while since I checked).
I'm more surprised by DXVK working cleanly
replyProton itself doesn't exist for macOS, but CrossOver already existed instead, which is mostly the same tech, and indeed supports D3D either through DXVK over MoltenVK, or through Apple's D3DMetal.
replyTechnically there're just 3 layers: DXVK over MoltenVK over Metal. D3D8 and Vulkan here are just the APIs implemented by those adapter layers.
replyThere're some D3D implementations over Metal that could skip the Vulkan layer but none implement the old D3D8 so you'd still need another layer that implements e.g. D3D8 over D3D9-11. Also, DXVK and MoltenVK have got a lot of traction and fixes on their own, so they're probably the most accurate pipeline for D3D on Metal.