Last time I used Software Updater it updated packages and after finishing, displayed "However, Ubuntu 20.04.1 LTS is now available (you have 18.04)."
I clicked the [Upgrade ...] button but nothing happened. In the Terminal, typing
$ sudo do-release-upgrade
returned this message:
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
Both Ubuntu Software and Synaptic report that there are no updates/upgrades for Ubuntu 18.04.5.
What do I do now?