When I opened Wireshark, the section where you select which interface to capture from was blank and it said that "No interface can be used for capturing in this system with this current configuration."
Fortunately, the fix is easy. This worked for me on Linux Mint. It should work on Ubuntu as well.
Open a terminal and run:
You should see a screen like the one below.
Answer Yes, then run this command:
Finally, reboot or log off and back on.
All the network interfaces should be listed now and Wireshark should function as expected.