ok, you don't need to remove the nullethernet + ssdt, not sure they are still needed but it was to fix Apple services for system that don't have internal ethernet device.
So you really are talking about an external USB adapter. I have an USB-C ethernet adapter (Realtek) and it works just fine. You might want to check on your router settings. It picked up an IP, so I don't see why it won't connect to the internet.
According to your IOReg file, you also has an internal broadcom wifi, not sure why it's not showing in your screenshot.