This is categorized under Gnome but refers to MATE.
Locking the screen makes it go black, after which typing anything or moving anything takes me to a login screen. If the desktop has only been locked for a short while, entering my password unlocks it as expected.
However, if it has been locked for a little while (I'm unsure of the exact duration, but no more than 10 minutes) typing my password takes me to a lock screen which instead of being blank has the time and date up top. Typing anything or moving the mouse takes me to a second login screen. Entering my password there unlocks the desktop.
I notice that the desktop locks automatically after a few minutes of inactivity. Perhaps if the desktop is already locked at this time it is locked again?
Trisquel 8.0 support ended in April 2021.
Please open a new issue in case it remains on the current supported release.
Cheers!
Thanks, that worked.
I had this problem too, but I removed gnome-screensaver and it worked after reboot. Save your documents first if you remove the gnome-screensaver and then lock your computer, because you won't be able to get back in after the first login box.
Clarification: The "black screen" after locking is my screensaver, not a lock screen.