I'm using Ubuntu 18.04 on a Dell XPS laptop. Half of my disk is Windows, the other half is Ubuntu.
When I reboot, I get the little triangular guy in my top right indicating that I have Ethernet but then after a while I find myself on WiFi and when I go to my Settings > Devices > Thunderbolt it says nothing detected and when I go to my network it doesn't seem to find anything related to my Ethernet.
Any thoughts?