kubuntu 18.04 on MSI Laptop GTX 1070 black screen on login with mouse cursor

After a new installation of Kubuntu 18.04 i have the following problems:
The system apparently starts OK, but the login screen remains black.
The mouse pointer is operable. Everything else I do from the ttys.

Sorry, how can i attach the complete nvidi-bug-report.log ?
nvidia-bug-report.log (673 KB)

Hovering the mouse over an existing post will reveal a paperclip icon to attach files. Next to it is a pencil icon which lets you edit your post and delete that WoT.

First of all excuse my bad English.
This is my first troubleshooting in this forum.
I’ve been trying to find a solution with the search function - unfortunately without success.
Maybe it could be sddm, but I found no error message in the log.

@ masemic

  1. Do you have a hybrid GPU laptop ?

  2. Are you running in secure boot ?

masemic,
please delete /etc/X11/xorg.conf
It’s for an Optimus (hybrid) notebook but yours is discrete-only. Afterwards, reboot and report back. Otherwise, everything else seems to run fine. So I suspect sddm somehow not working. If you find its logfiles, post those. Or maybe try to switch to lightdm.

You could check if sddm writes logs to journal:
sudo journalctl -b 0 _COMM=sddm --no-pager

Because of another bug, it was faster to reinstall.
After that, the system starts normaly.
Thank you all.
For the next problem (with twinview - sddm does not accept an entry) I start a new thread.