I switched from Ubuntu 18.04 LTS to Ubuntu 19.04, and accidentally removed HWE packages related to X.Org Server left from 18.04.
After that I'm getting stuck on the login screen. That is, after I click my user account and enter my password, I am being returned back to login screen.
I already installed back those packages, reinstalled & reconfigured
xserver-xorg, installed old NVIDIA drivers. Nothing helped.
startx returns no errors
X.Org X Server 1.20.4 X Protocol Version 11, Revision 4 Build Operating System: Linux 4.4.0-143-generic x86_64 Ubuntu Current Operting System: Linux mirage 5.0.0-25-generic #26-Ubuntu SMP... ... Build Date: 03 April 2019 09:03:57AM xorg-server: 2:1.20.4-1ubuntu3 Current version of pixman: 0.36.0 ... Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) informational, (WW) warning, (EE) error, (NI) not implemented, (??) unknown (==) Log file "/var/log/Xorg.1.log", Time: Fri Aug 23 14:25:51 2019 (==) Using config file: "/etc/X11/xorg.conf" (==) Using system config directory "/usr/share/X11/xorg.conf.d" xinit: connection to X server lost waiting for X server to shut down (II) Server terminated successfully (0). Closing log file.
UPD. Reinstalled system. Everything works now. Thanks for your help!