I have air gapped systems with Ubuntu 22.04 desktop. I get a red circle exclamation point. If I click, I get "the update information is outdated. This may be caused network problems or ..."
The problem is that these computers should never be connected to the Internet and updated. Using a mirror also isn't an option. Using apt-offline isn't an option. The computer is supposed to remain isolated -- no network, no USB but does have a KB, mouse and RS-232 serial to a lab device.
My research has only found solutions that involve connecting to the Internet, disabling repos no longer available, fixing broken packages, etc. None of those fit the problem.
I also tried seeing if the message could be disabled from its own menu. After clicking the icon, I selected preferences. This results in the program crashing. That temporarily gets rid of the annoying icon but it will return in a few days.
What I want is for the alert/message to go away and never come back.