Ubuntu server: The list of available updates is more than a week old

When I log into my Ubuntu server via SSH, a "Welcome" text is displayed. This text used to contain information about packages avilable for update.

Since some time, always the text "The list of available updates is more than a week old." is displayed instead.

Of course, I regularly check for updates with "sudo apt update". This has no effect on the text on the "Welcome" screen.

Does anybody what's wrong there and how to fix it?

I filed this bug report: https://bugs.launchpad.net/ubuntu/+source/update-notifier/+bug/1943638

I have also described a workaround there.

[Edit] Description of the workaround:

In my case, an uncaught exception in line 150 of the file /usr/lib/update-notifier/apt_check.py was the cause.

I fixed this by adding a try...except block around it.

Original code:

    is_esm_supported = bool(
                DISTRO in ubuntu_distro.supported_esm()

Modified code:

    try:
        is_esm_supported = bool(
                DISTRO in ubuntu_distro.supported_esm()
    )
    except AttributeError:
        is_esm_supported = False

The script source of the message (Ubuntu 20.04?) seems to be from

/etc/update-motd.d/90-updates-available

The actual problem (for me) is that

/var/lib/update-notifier/updates-available

is older than 7-days and should be pretty much empty. I achieved that by

echo | sudo tee /var/lib/update-notifier/updates-available

I tried Thomas1970 suggestion (good year, by the way) and it made zero difference.

I then looked at the file:

sudo nano /var/lib/update-notifier/updates-available

It had the line "The list of available updates is more than a week old." inside. I tried using "#" to block the display but that didn't do anything except print "#" in front of the line.

Next, I erased the content of the file and rebooted.

"The list of available updates is more than a week old." is now gone. I am awaiting further updates to see if I get notifications at login, as Thomas1970 thinks zeroing the file would prevent future update notifications.

I have remmed out the Thomas1970 fix in /usr/lib/update-notifier/apt_check.py for now to see what happens.

For now, my solution at least fixes the notification issue. I continue to do a sudo apt update whenever I log in to my server.