MacRumors:

Apple’s new M1-equipped MacBook Air, MacBook Pro, and Mac mini do not appear to be compatible with eGPUs, including the Blackmagic eGPU that Apple has promoted alongside other Macs and that is available through the online store.

Apple will add support for eGPUs at some point only if the integrated GPUs lag terribly behind what ATI is doing now. If you’ve gamed on an iPad Pro, you know that Apple’s silicon is more than adequate–even if it’s not top-notch gamer kit. Apple is describing it as the fastest integrated graphics in a personal computer– a metric not interesting to hardcore gamers, but serviceable for those of us paying too much money for eGPUs with last year’s boards.

M1 MacBook Air, MacBook Pro, and Mac Mini Not Compatible With eGPUs