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:
ubuntu-support-status
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:
The three computers on which I now run Ubuntu MATE are 32 bit machines. Are these computers supported by Ubuntu MATE 20.04 LTS. If not, what do I do now?
Well, that officially kills off 32 bit architecture for Ubuntu in general. At least there’s Debian that still supports it though.
not exactly surprised though. I do have some 32 bit computers laying around though, and Ubuntu was one of the first Linux distributions I ever took a look at. In fact, my middle school’s tech recommended it to me all the way back in 2010, and I’ve been experimenting with Linux ever since.
Thank you very much for your attention. But I think, that having an old machine, with i386 (32bit) architecture, I cannot update or I think I cannot, to Ubuntu Mate 20.04 Ltd. distributions. If I am wrong, I ask you to inform me.
The Linuxium guy graciously has provided a premade ISO that you can download to test whether it may work for your computer (please donate to him if you find the ISO/script useful) . I installed a respun Ubuntu Mate 20.04 on my 2007 Mac mini and it has worked great for many months. If it boots I am sure you will be able to install it.
You can install Ubuntu using that ISO, and then you have a Linux machine you can respin other distro's using the Linuxium script. I did Elementary OS and Peppermint OS without problems.
Perhaps there is a terminal command to check if its capable to run 64 bit software?
Since we'll no longer receive security updates and patches how is it that, "Your system will still be as secure as the Ubuntu base until April 2023"?????
I have been using Ubuntu 18.04 for a few years. Used Unity DE initially but then moved to gnome and finally to Mate DE 1.20.1 I guess that may technically not be the same thing as using Ubuntu Mate 18.04 because I added Mate to my already running Ubuntu 18.04.
Now, I have no other reason to upgrade the base OS to Ubuntu 20.04 (and would like to avoid doing that as much as possible) so am looking at options to see if I can continue with higher/supported versions of Mate DE with my existing Ubuntu 18.04.
I am interpreting this announcement to mean that this is not possible, and if I want to continue to use fully supported Mate DE (like 1.24?) I must upgrade the base Ubuntu to 20.04.
To my understanding: The basic parts of the Ubuntu system will continue to be upgradeable until April 2023. That means that packages will continue to get security patched, but applications in general will not get upgraded per se; you can expect the system to stay secure for two more years, but you will not see any packages' version numbers increasing, only security fixes from newer versions of the software getting applied to the old stuff. So security holes will be closed, but features will not be added.
In the same vein, I think that software from the universe and multiverse repositories will not get official security patches applied to it, either. The latter probably doesn't make a difference to most of us; barely any software is available from the multiverse. But a lot of software, including the MATE Desktop applications, come from the universe and as such won't be seeing many, if any, security updates. Now, chances are any software you have installed from the universe isn't critical server software that needs to stay updated; but caveat emptor if you do install software from the universe or multiverse that is security-critical.
TL;DR: Generally speaking, stuff in the main and restricted repositories get security fixes; stuff outside those repositories does not after this point.
Interesting side note: I was surprised to see that the core command-line packages for Ubuntu 21.04 Beta have been compiled also for 32-bit i386 machines. I would have guessed Ubuntu would have totally discontinued support for these archaic systems by now. Of course, you still can't install any graphical applications on Ubuntu 21.04 i386, limiting the potential here. But as @franksmcb already noted above, it's entirely possible to use Debian instead; I use Debian on a regular basis too and absolutely adore it and swear by it, and readily recommend it to anyone using Ubuntu (MATE) 18.04 on 32-bit hardware.
I have a old 32-bit, 1Gb RAM IBM Thinkpad x40 that is running UM 18.04 32bit.
I really like this computer. It's now a 30 years old artifact but do not have any scratches, work good and silently, the battery is able to let you work for 3 hours without power supply, and the machine is much slimmer than some of today computers.
Sometimes, I'm asking myself how it's possible that the feeling is that this old computer goes faster then my other modern 64bit 4GB memory laptop.
Unfortunately the technologies go in front, and leave such devices behind.
It is not possible for developers, software editors, and security teams to maintain 32 bit anymore ...
The HW is missing today standards for optimal work, the network interfaces uses very old drivers that conflict with some modern software. The wireless card is not able to see modern wifi hotspots (the protocol changed). You default browser stops working on it ...
This computer can still help doing some things, like ssh somewhere, read a post on a forum, burn a CD ... but as in near feature packages like openssh-server will not receive updates, this will potentially open huge security risks, and can lead to a data leak or even worst.
I will continue using this machine for cool stuff, but never for work or critical data processing.
I would upgrade from 18.04 but 18.10, 19.04, 19.10, and 20.04 break code that works in 18.04. For example - I watch videos on YouTube. 20.04.2 adds severe noise to the audio stream. It is not the hardware or the settings because it works fine when I reboot to 18.04. If you would actually check your code before releasing it I would upgrade.
All releases are QA-tested, it's a volunteer effort, and the people doing it use whatever hardware they have available to them.
With more people stepping up to help, more issues may be detected, bugs raised & fixes worked out, but if issues aren't reported as bugs on a bug tracker (and also ideally testing-tracker), they don't exist (and for sure can't be fixed).
To me I get the feeling you have an issue with the kernel (18.04 using the GA kernel uses 4.15), 18.10 used 4.18, 19.04 used 5.0, 19.10 used 5.3 & 20.04 uses 5.4 (using GA stack) all of which are HWE kernels for 18.04). I had some [vintage] 2004 laptops (IBM Thinkpad r50p, t42p) that have issues with the 5.4 kernel but were fine on earlier kernels. Kernels are not a Ubuntu-MATE issue, and the issues I'm talking about occur on any flavor I tested.
Either way, all Ubuntu-MATE systems are QA-tested, and if you'd like to step up and help, that would be greatly appreciated
sorry but this sounds to me as HW and SW problem. What i think is happening you have a driver/kernel issue which can sadly happen and we cannot check for every HW piece that is available on the market. Every release is heavily tested by our QA team but again not everything is available to us, may i recommend that you try another 20.04 release of ubuntu like mainline or something like that and see if same bug persists
System Monitor and checking the System tab.
To continue the retrospective future , we recommend upgrading to Ubuntu MATE 20.04 LTS or later.
Software Updater and follow the steps. Alternately, via the 
Terminal:
