As of 30 April 2021 Ubuntu MATE 18.04 LTS has reached EOL (End of Life) and is no longer supported. There will be no more updates or security patches for this release.
Being a long term release (LTS), official Ubuntu flavors are only supported for 3 years, as opposed to Ubuntu's 5 years. This means MATE components of your system will no longer receive updates after today, but foundational components will continue to receive security updates from Ubuntu.
Please note that there is no upgrade path for i386 (32bit) systems.
How do I check?
See which version you are running by opening the System Monitor and checking the System tab.
To check the support level of your system, run this command in the Terminal:
What should I do?
To continue the retrospective future , we recommend upgrading to Ubuntu MATE 20.04 LTS or later.
If you're still running 18.04 LTS and are not ready to upgrade, don't panic! Your system will still be as secure as the Ubuntu base until April 2023, but please bear in mind some of your packages and applications will no longer receive updates.
To upgrade, open Software Updater and follow the steps. Alternately, via the Terminal: