https://wccftech.com/you-cant-customize-the-m1-mac-mini-with-10gb-ethernet-but-you-can-buy-a-thunderbolt-3-dongle-to-correct-the-situation/

As we dig into the new M1 Macs, we are learning new things on the fly. For example, you can't configure the new Mac mini with 10Gb Ethernet.

While the new Macs with M1 are blazing fast compared to previous-generation models, not everything is amazing. Take a look at the Mac mini for example, while it does pack a lot of bells and whistles in the performance department, but it completely chickens out on the Ethernet port front.