Apple provides network connections via Wi-Fi or using this for wired connections.
https://www.apple.com/shop/product/MD463LL/A/thunderbolt-to-gigabit-ethernet-adapter
There are issues we have seen with the release of Big Sur and are in the process of identifying the causes. Here is a search showing some of the feedback we have been getting.
https://forum.lightburnsoftware.com/search?q=Big%20Sur%20OS%20%40LightBurn%20
To quote Oz, from a few days ago,