You probably ran an update before this and updated the screen locker. Then the OS was in a mismatched that caused the screen locker to break.
Fedora Linux
All about Fedora Linux
Yes, I get this regularly on my piece of shit work HP laptop running Ubuntu. It doesn't handle my USB dock well.
Try to do as it says, although it sometimes gets the session number wrong and maybe the F-key too.
Once, in a Debian work machine. Did as it said, worked flawlessly afterwards.
Getting it all the time on Fedora KDE. And Ctrl+alt+F1 (or any other F key) doesn't get me to a terminal and even SSHing into the computer and entering the command doesn't get rid of it (update: I tried the SSH method again and it worked). Been just turning the computer off and on again whenever it shows up.
I think an update broke something and am hoping it gets fixed soon.
Depending on your setup F1 might be occupied. (GDM takes it up on mine) You can try F3-F6 as iirc most distros have 6 ttys
I was able to fix it on my machine by switching from the fedora to the breeze theme
I'm on Aurora (which is based on Fedora silverblue) and after updating, I started getting that error (yesterday).
Followed the instructions and got back in, but earlier today when I manually locked the PC, I didn't get the error screen, just a mouse and black screen. Followed the same instructions to get back into my desktop.
It's already been reported as a bug, and I think a new update should fix it really soon.
I got it for the first time today, fixed it rebooting the machine. I hope it doesn't become a common occurence.
Happened once yesterday while setting up and updating Fedora KDE on a 2012 MacBook Pro 9,2. Haven't had it happen since then so I hope it was just a hiccup while I was getting it all up to date