Ubuntu Software thinks it is offline – using netplan to manage networking

This has been the bane of my existence for some time until I finally decided to investigate and resolve this issue on my server in order to install proprietary Nvidia drivers through the Additional Drivers dialog.

The below netplan config shows my original config. After some googling, this post alerted me to the fact that my config is missing the renderer key.

network:
  ethernets:
    eno1:
      addresses:
      - 10.1.1.2/24
      gateway4: 10.1.1.1
      nameservers:
        addresses: [10.1.1.1]
        search: []
    enp79s0:
      optional: true
      dhcp4: true
    ens4:
      optional: true
      dhcp4: true
  version: 2

The render key allows netplan to play nicely with Network Manager and populate network interfaces in there.

network:
  renderer: NetworkManager
  ethernets:
    eno1:
      addresses:
      - 10.1.1.2/24
      gateway4: 10.1.1.1
      nameservers:
        addresses: [10.1.1.1]
        search: []
    enp79s0:
      optional: true
      dhcp4: true
    ens4:
      optional: true
      dhcp4: true
  version: 2

As soon as I added this key and tested/applied the configuration with sudo netplan try and sudo netplan apply, it resolved the issue for me.

Ubuntu software is now aware of the internet connection and is able to retrieve software repository information and updates.