Lubuntu 18.04 is based on LXDE, not LXQt, and so it uses lightdm, not sddm. greeter is lightdm-gtk-greeter, which causes traps in libglib like these :
ноя 04 16:50:48 user-desktop kernel: traps: lightdm-gtk-gre[673] trap int3 ip:b6f929d0 sp:bf9e9e20 error:0 in libglib-2.0.so.0.5600.4[b6f44000+12e000] ноя 04 16:50:52 user-desktop kernel: traps: lightdm-gtk-gre[736] trap int3 ip:b6fe49d0 sp:bfbcfcd0 error:0 in libglib-2.0.so.0.5600.4[b6f96000+12e000] ноя 04 16:50:54 user-desktop kernel: traps: lightdm-gtk-gre[798] trap int3 ip:b70149d0 sp:bf839010 error:0 in libglib-2.0.so.0.5600.4[b6fc6000+12e000] ноя 04 16:50:56 user-desktop kernel: traps: lightdm-gtk-gre[860] trap int3 ip:b70669d0 sp:bf9a2f40 error:0 in libglib-2.0.so.0.5600.4[b7018000+12e000] ноя 04 16:50:57 user-desktop kernel: traps: lightdm-gtk-gre[922] trap int3 ip:b701a9d0 sp:bfe9c750 error:0 in libglib-2.0.so.0.5600.4[b6fcc000+12e000] ноя 04 16:50:59 user-desktop kernel: traps: lightdm-gtk-gre[984] trap int3 ip:b6fa19d0 sp:bfb4dcb0 error:0 in libglib-2.0.so.0.5600.4[b6f53000+12e000]
Lubuntu 18.04 is based on LXDE, not LXQt, and so it uses lightdm, not sddm. gtk-greeter, which causes traps in libglib like these :
greeter is lightdm-
ноя 04 16:50:48 user-desktop kernel: traps: lightdm- gtk-gre[ 673] trap int3 ip:b6f929d0 sp:bf9e9e20 error:0 in libglib- 2.0.so. 0.5600. 4[b6f44000+ 12e000] gtk-gre[ 736] trap int3 ip:b6fe49d0 sp:bfbcfcd0 error:0 in libglib- 2.0.so. 0.5600. 4[b6f96000+ 12e000] gtk-gre[ 798] trap int3 ip:b70149d0 sp:bf839010 error:0 in libglib- 2.0.so. 0.5600. 4[b6fc6000+ 12e000] gtk-gre[ 860] trap int3 ip:b70669d0 sp:bf9a2f40 error:0 in libglib- 2.0.so. 0.5600. 4[b7018000+ 12e000] gtk-gre[ 922] trap int3 ip:b701a9d0 sp:bfe9c750 error:0 in libglib- 2.0.so. 0.5600. 4[b6fcc000+ 12e000] gtk-gre[ 984] trap int3 ip:b6fa19d0 sp:bfb4dcb0 error:0 in libglib- 2.0.so. 0.5600. 4[b6f53000+ 12e000]
ноя 04 16:50:52 user-desktop kernel: traps: lightdm-
ноя 04 16:50:54 user-desktop kernel: traps: lightdm-
ноя 04 16:50:56 user-desktop kernel: traps: lightdm-
ноя 04 16:50:57 user-desktop kernel: traps: lightdm-
ноя 04 16:50:59 user-desktop kernel: traps: lightdm-