Ethernet not working well in Ubuntu 18.04 on new desktop

The solution is available at this off-SO link.

In summary, here is what I did that solved the issue.

1. Inserted a WiFi USB dongle and connected to the WiFi router, and tested that internet connection is working.
2. Did: sudo apt-get update
3. Did: sudo apt-get install r8168-dkms to install the r8168 kernel driver (suppressing the r8169 driver that came default with the kernel)
4. Reboot the PC
5. After reboot the Wired Ethernet started working.