Maybe not mandatory, but do a ‘sudo reboot’ in terminal after ‘sudo upgrade’ then run the updater application.
Unfortunately, I can’t get access to the “The software on this computer is up-to-date” screen, because I have a bunch of grayed-out / disabled “Ubuntu Pro security updates” which I have not installed:
How can I trigger the updater GUI manually?
EDIT
I ran this command from the terminal to trigger the update GUI:
sudo do-release-upgrade -f DistUpgradeViewGtk3