Ubuntu 20.04 - Realtek Ethernet failed after restarting the system
Ubuntu 20.04 - Realtek Ethernet failed after restarting the system
It seems you're stuck in a tricky situation. The usual fix for resetting the network manager involves removing its config files, deleting it from your system, and then reinstalling it—but that won't work without internet access. This creates a loop. You might be new to networking, so understanding basic steps could help. If you're unsure, setting up a static IP address is another option you can try.
It seems the cable wasn't visible and the device isn't functioning.
Full RTL8125 compatibility was introduced in Kernel 5.9. Consider upgrading your kernel and installing the newest Linux firmware tree.