I could not get my Mac to successfully do anything with the script from their GitHub; set device to mps, downloaded llama for the first time in a year, and it just .. hangs. I presume this is sortable, but I'm not sure I care enough.

All that said, I think it likely this has been built and trained only on Nvidia

This is bound to be a question that will be increasingly harder to answer. For instance, Apple processors have at least two different neural accelerators/matrix coprocessors (ANE and AMX) in addition to the integrated GPU. Do these count as "CPU"?

Why would you want to? It's like using a hammer for screws.