There are Thunderbolt 3 10gbit adapters that work on M1. I use a QNAP QNA-T310G1S on an M1 Mini with no issues. It's SFP+, which I prefer--both due to existing hardware I already have, and for lighter power consumption compared to 10gbit over RJ45.

QNA-T310G1T is the RJ45 model, but there are other makes available too.

(I bought the Mini at launch, and they've since released a SKU with built-in 10gbit Ethernet)