The Mac Pro still has auxiliary power connectors, so you could theoretically install a GPU in it, just not the highest end ones. No drivers so you can't really do anything with them. I do suppose Nvidia could maybe do CUDA drivers for a card, but would Apple even allow it?
@paul WTH, How many watts do GPUs take now?? I haven't bought a separate GPU for nearly 20 years…
@pixel @paul Same, last time I assembled a PC was in 2004, and then a few years later I switched to Macs - I'm now looking for a Windows computer for my sister, and apparently the GPU is now half the cost of the whole box 😐