Comment 0 for bug 2024892

Both Trisquel and Ubuntu MATE 23.04 ships with the package `update-notifier` (apt-cache show update-notifier: "Puts an icon in the user's notification area when package updates are available.") -- see the orange icon in the bottom left on the screenshots for "Trisquel" below.

The distros also have these settings in common:
* MATE Panel item: The update-notifier icon is also put on _Indicator Applet Complete_ ("A unified applet containing all of the indicators.") that is installed by default. However, the update-notifier icon is also put on _Indicator Applet_ ("An indicator of something that need your attention on the desktop"), that can be added manually.
```
$ gsettings list-recursively com.ubuntu.update-notifier
com.ubuntu.update-notifier end-system-uids 500
com.ubuntu.update-notifier no-show-notifications false
com.ubuntu.update-notifier notify-ubuntu-advantage-available false
com.ubuntu.update-notifier regular-auto-launch-interval 7
com.ubuntu.update-notifier release-check-time uint32 1686523321
com.ubuntu.update-notifier show-livepatch-status-icon false
```

#### Expected behaviour
`update-notifier` should put an icon in the panel for Ubuntu MATE.

#### Actual behaviour
`update-notifier` will put an icon in the panel for Trisquel, but not for Ubuntu MATE.

#### Steps to reproduce the behaviour
* Make sure that the distro is outdated (can be done by installing them from scratch in virt-manager, without internet connection).
* On the first boot run: sudo apt-get update && reboot
* reboot again