I would be interested in helping to port Cycles to MacOS using Metal (since I’ve heard OpenCL problems seem to have caused MacOS GPU support to be dropped). I’m an experienced graphics programmer, and have been implementing a lot of compute kernels on MacOS with Metal recently (though mainly for cryptography and AI). I did a lot of CUDA a number of years back. I haven’t really looked at the cycles code so far so I would need a bit of time to get up to speed (and/or some assistance).
I’m starting to get some experience with Vulkan compute as well, though that hasn’t been a priority yet. But it should pay off if a port to Vulkan is desired as well.
FYI, up until it was disabled Cycles GPU rendering on my Mac was working fine as long as I disabled the AMD GPU (the Intel one worked fine). Sorry to see it go.