Well, Nvidia (outside of some really, really old hardware) isn’t supported on Mac so I’d imagine effectively M1 doesn’t support CUDA.

I would hope they didn’t kill off eGPUing Radeon cards, but I haven’t kept track of the new hardware other than M1 being really good.

They didn't. But there are no driver available for Radeon cards on M1, so for now it is effectively dead.

EGPUs aren’t supported for the M1, but Big Sur still identifies and connects to them, implying Apple may restore this feature in the future.

I saw this mentioned recently that they are just missing drivers. Which this being ealy days for Apple Silicon makes sense.

I think eGPUs require a thunderbolt connection, which IIRC is only supported by Intel processors

The new mac's ship with USB4/Thunderbolt ports - it's now a cross-platform port (USB4 is a merger of sorts between USB and Thunderbolt)

https://www.tomshardware.com/news/usb-4-faq,38766.html

Apparently Thunderbolt is full of low-level x86 quirks, so getting existing devices working on ARM Macs is likely to be a punishingly heavy lift even for Apple, which seems to have barely started work. And of course Intel isn't likely to be all that co-operative. https://level1techs.com/video/can-apple-do-thoughts-armthund...

Apple is the developer of thunderbolt,They wrote the specifications for it and there are two thunderbolt ports on every M1 Mac

Intel invented Thunderbolt as LightPeak. Apple developed it further in cooperation with Intel.

You are right. I forgot about LightPeak, which was designed to work over optical cables.

Apple came in when Intel decided to build a version for standardized cables, and helped Intel develop the spec (and even supplied the name).

But my point remains. Apple knows Thunderbolt as well as Intel does by this time.

There is one AMD motherboard I’ve seen with a TB3 port. ASRock I think makes it?