In elementary OS 5
Distributor ID: elementary
Description: elementary OS 5.1.7 Hera
Release: 5.1.7
when nvidia-340 driver is enabled, after an user has logged in to the graphical environment, it is impossible to log in as a different user: after a blank screen, lightdm is proposed again (only the first user can successfully login). Remarkably, after the attempt, the resolution of lightdm is lower than the usual one. If nouveau driver is in use, the process is flawless. Below is the (IMO) relevant part of /var/log/syslog after trying to login as 2nd user.
Aug 25 15:00:08 cassisa-PC at-spi-bus-launcher[3777]: dbus-daemon[3782]: Successfully activated service 'org.a11y.atspi.Registry'
Aug 25 15:00:08 cassisa-PC at-spi-bus-launcher[3777]: SpiRegistry daemon is running with well-known name - org.a11y.atspi.Registry
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: X Error of failed request: BadValue (integer parameter out of range for operation)
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: Major opcode of failed request: 151 (GLX)
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: Minor opcode of failed request: 3 (X_GLXCreateContext)
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: Value in failed request: 0x0
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: Serial number of failed request: 19
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: Current serial number in output stream: 20
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: gnome-session-check-accelerated: GL Helper exited with code 256
Aug 25 15:00:08 cassisa-PC gnome-session-c[3788]: eglInitialize() failed
Aug 25 15:00:08 cassisa-PC gnome-session[3660]: gnome-session-check-accelerated: GLES Helper exited with code 256
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: X Error of failed request: BadValue (integer parameter out of range for operation)
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: Major opcode of failed request: 151 (GLX)
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: Minor opcode of failed request: 3 (X_GLXCreateContext)
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: Value in failed request: 0x0
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: Serial number of failed request: 19
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: Current serial number in output stream: 20
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: gnome-session-check-accelerated: GL Helper exited with code 256
Aug 25 15:00:13 cassisa-PC gnome-session-c[3794]: eglInitialize() failed
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: gnome-session-check-accelerated: GLES Helper exited with code 256
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: gnome-session-binary[3660]: WARNING: software acceleration check failed: Processo figlio uscito con codice 1
Aug 25 15:00:13 cassisa-PC gnome-session-binary[3660]: WARNING: software acceleration check failed: Processo figlio uscito con codice 1
Aug 25 15:00:13 cassisa-PC gnome-session[3660]: gnome-session-binary[3660]: CRITICAL: We failed, but the fail whale is dead. Sorry....
Aug 25 15:00:13 cassisa-PC gnome-session-binary[3660]: CRITICAL: We failed, but the fail whale is dead. Sorry....
Aug 25 15:00:13 cassisa-PC at-spi-bus-launcher[3777]: XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":1"
Aug 25 15:00:13 cassisa-PC at-spi-bus-launcher[3777]: after 21 requests (21 known processed) with 0 events remaining.
