In the end, I think what went wrong was that the device didn’t have enough disk space, so when I upgraded the l4t, the ugrade didn’t work properly and caused some kind of problem with the network connection of the agx.
I was able to connect the device to a host machine with Ubuntu 18.04 and download and use the sdkmanager to flash the system with Jetpack 4.6 using the proper usb-c 3.1 and a monitor, mouse and, keyboard.
After the new flash was properly completed and the device was set up, the ethernet connection is working great.