Update on this:
Plugged in both types of adapters and they each pull different addresses but when waiting for interfaces come back up, Fog gets confused and displays the same error. I was able to find n Amazon-branded (Cable matters) usb3 to ethernet adapter and tried with that. Success.
I’ve ordered USB-C to Ethernet from the same vendor, I’ll update this as soon as I get that one tested.
With all of this said, I did build a custom kernel with the original USB-C adapter from Dell and that still didn’t want to work.