10Gb ethernet from 2020 MB Air M1

The only way to connect a 10 Gigabit Ethernet adapter would be through one of those ports.

Probably via Thunderbolt 3, since USB 3.1 Gen 2 tops out at 10 Gbps before overhead, and the USB4 20 Gbps and 40 Gbps transfer modes are relatively new.

These adapters are not cheap, but you can get some for less than $300 USD.

Sabrent has one for $160. B&H Photo Video and Adorama both list it on their sites.

Sabrent – Thunderbolt™ 3 to 10 Gigabit RJ-45 Adapter TH-S3EA

B&H Photo Video – Sabrent TH-S3EA Thunderbolt 3 to 10G Ethernet Adapter

Adorama – Sabrent Thunderbolt 3 to 10 Gigabit RJ-45 Ethernet Adapter

Adorama says it is "Compatible, but not optimized for Apple M-series Macs." You would need to ask them what they mean by that.

Other World Computing has one for $200:

Other World Computing – Thunderbolt 10G Ethernet Adapter

SonnetTech has one for $200 (the Solo 10G):

SonnetTech – 25Gb, 10Gb, 2.5Gb, and AVB Ethernet Thunderbolt Adapters

There may be others.

it should be possible the thunderbolt 3 ports should provide the right bandwidth but make sure to use a NIC (network interface card) compatible with MacOS and when it comes to a cheaper alternative you may be able to use a old thunderbolt to pcie adaptor/enclosure to use a normal NIC with rj45 but I would't recommend buying a whole new thunderbolt to pice adaptor because with the NIC the price would be very close if not more then $300 and unless you want to use it as a nas or just to see if it works you probably don't need 10Gb on a finless m1 MB air

if you are going to use it as a nas you can use a usb hub with PD a and hook up usb raid arrays or HDDs and SSDs and you can raid them in disc utility

They are not quite that expensive.

https://www.owc.com/solutions/thunderbolt-3-10g-ethernet-adapter