I have a 2018 MacBook Pro, and right after I updated to Catalina, the
Thunderbolt-to-ethernet interface stopped working. I have two docks and a
third-party usb-c gigabit ethernet adapter, and none of them work now.
The docks are Cable Matters model 107024 Thunderbolt docks, and the
adapter is a Techkey usb-c to ethernet adapter.
Haven't tried it with an Apple adapter yet, as I don't have one available.