A piece of software with a bug in it can do absolutely anything, it is unpredictable.
It perhaps interfered with you video card settings.
Anyway lets celebrate the fact that it was not a hardware problem.
Oh, and a gentle reminder. Get a decent backup system going.
Cheers
Neville
This is definitely newsworthy. How in the world can a Welcome Screen make an entire operating system practically unusable?
Judging from the symptoms you experienced, I was thinking about a serious hardware issue based on the storage medium you are using.
It’s horrendous to know that even such seemingly simple & small things can break the entire Linux GUI.
Pretty much a Linux GUI killer.
No. A Welcome Screens shouldn’t make the entire operating system not work. Just Linux GUI things…
It seems like only Linux GUI is able to break the entire operating system just because of a simple Welcome Screen. 
Yes, everyone will definitely need that, because in Linux GUI, you literally only need a Welcome Screen for your entire operating system to become unusable.
The next time, someone says, his Linux GUI “just works”, I will always repost this story to make clear how it just does not work.
Simple. It just has to get a memory violation and it can write on anything. I know, the OS is supposed to trap a segmentation fault, but I dont think you can rely on that. For example, it might be running something in the GPU, and that is outside of memory management.
If it’s that simple, it would happen on every operating system, just like Linux GUI.
It’s not that simple, though. Never heard of something like this happening on macOS and in all these years never had the Welcome Screen of any Windows version crash – not to mention making the entire OS unusable.
If something on Windows is causing such a problem, it will just crash and Windows will keep working. No problem. You can even work without the Explorer, if necessary.
Because apparently Linux GUI is too stupid to handle it, just as naturally as other GUI operating systems.
This only happens on Linux GUI, though, so still does not matter and is not an argument.
what is this welcome screen thing?
Are we talking about the Display Manager?.. gdm or sddm or…?
The little thing that breaks the entire Linux GUI, just like that, without any effort, because Linux GUI is too stupid to handle a problem with such a little thing.
I dont understand Welcome Screen.
Is it some part of a snap package?
This topic has been about a serious issue causing Linux GUI to become unusable.
Finally, it was found out, that a Welcome Screen on Linux GUI is causing this issue.
So, you tell me what Welcome Screen it is.
The Welcom screen ( whatever that is ) is the cause of the problem. The Linux gui is just not robust enough to ride out the problem, but it is not the cause of the problem.
Yes. Because Linux GUI is too damn stupid to handle a simple & small piece of software failing.
I also do not understand your questions regarding a Welcome Screen. It does not matter at all, what kind of Welcome Screen it is. The whole point is, that such a small piece of software can break the entire Linux GUI, because Linux GUI is inherently broken and most of the time does not work the way it should.
It does matter.
This stupid small piece of software might be bypassing the Linux GUI altogether and dealing directly with hardware. That would cause many issues, and the GUI would be powerless to stop it. I doubt if the Win or Mac gui could stop that either
Why does Linux GUI let that happen then?
No matter, how far we go into detail. Linux GUI is the stupid dumbnut here.
Additionally, I doubt that a Welcome Screen is doing some werid shady shit…
Woulda shoulda coulda. Never happens on Windows or macOS. Happens on Linux GUI all the time with several tiny shits, because Linux GUI is as dumb as possible.
Boys, boys, calm down!
First, the Welcome Screen (search for Ubuntu Mate Welcome) is SUPPOSED to come with the upgrade. It did not. Strike One for the Mate team.
Second, I wanted it because I could not find Desktop Layout easily without it. Themes, yes, layout no. Strike Two for the Mate team.
Third, I found how I could get it back, and that was by installing with the dreaded snap:
snap install ubuntu-mate-welcome --classic
Strike One for snap
And now, here on the ITSFOSS website in Firefox, I cannot upload a picture. Instead, I have the error message:
Could not read contents of etc
Hmmm. Is that related?
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It could be doing a simple probe of the video card, and getting it wrong.
Maybe @clatterfordslim is right, this welcome screen comes from a snap product. It might be trying to make itself independent of the linux environment by probing the hardware, instead of looking at the linux settings.
Then Linux GUI should prevent that from destroying the entire operating system. As I already said previously, going more into detail will just confirm Linux GUI’s ignorance.
The GUI is not a police force. That is the kernels job
That happens every Sunday night. Its some FOSS issue?
You know exactly from all the discussions we had previously, that when I say “Linux GUI” I am referring to a GNU operating system based on Linux, which is using a graphical user interface, which is meant to be used by humans.
Therefore, you know that I do not expect the GUI itself to take any responsibility, whatsoever.
I am talking about how Linux is just incompatible with human GUI, because all the issues are rooted in the elitist mindset of many Linux related maintainers.
I can do it in Mint, different browsers.
At this point, I do not know how often I will keep trying to make Ubuntu Mate work, so do not expect me to go into it and try uploading that image again. Th error message struck me as mighty peculiar.