A Blender Eevee/Viewport module meeting took place today as their weekly sync around development efforts. It was noted that the Metal back-end can now be enabled with Blender 3.5 development builds via the program's user preferences. So far there have been no show-stoppers reported but does not currently support viewport compositing. There are also some patches needed still for Metal on Intel and AMD graphics hardware for fixes/workarounds. In any case, the Apple Metal code is planned to be a secondary back-end for the Blender 3.5 release.
Blender 3.5 entered its "improve and stabilize" phase last week while at the start of February is when it will transition to its bug-fixing only stage. The Blender 3.5 stable release is expected for 15 March.
While the Metal back-end should be in decent shape for Blender 3.5, the same cannot be said for Blender's work-in-progress Vulkan support. At today's module meeting they commented:
Upcoming month no activities have been planned for the Vulkan back-end. The goal for February would be to be able to compile and run a compute shader. This requires many different parts before this can be done. Linking shaders, descriptor sets, buffers and memory management.
Hopefully we'll see the Vulkan back-end take more appropriate shape this year for Blender. Granted, it would have been nice to see Blender target Vulkan initially and then leverage MoltenVK for running on Apple hardware with Metal, but among other reasons it's possible that move wasn't pursued due to Apple joining the Blender Development Fund last year and thus a vested interested in targeting Apple's compute/graphics API directly.
The latest Blender Eevee/viewport module details can be found via devtalk.blender.org .