Comment 21 for bug 1718658

Ok, so I restored my system and I got back to my Mate and all my settings are kept.
I did a lot of things, even removed ecryptfs while extracted all my home directory from it.
I removed NVidia drivers but I don't think that they caused the problem.
But only reinstalling of XServer finally resolved the problem. I did something like described here:
https://www.computersnyou.com/4945/re-install-xorg-xserver-completely-ubuntu/

Hint: if you get "Ubuntu Black Screen" then on GRUB item press "e" to edit menu item then replace "no splash" or "splash quit" with nomodeset and press F10.

Thus I think the problem was caused by some tricky X11 configs upgrade.