Xorg server 1.20.1 fails start using the 340.107 driver with kernel 4.18.0-10. (Cosmic RC testing)

In Kubuntu 18.10 Cosmic RC, SDDM fails to launch using NVidia driver 340.107 (Dell M1530 laptop, 8600M GT). Dropping to a terminal (ctrl-alt-f2) and running startx proceeds to the Kubuntu desktop. Laptop boots into SDDM using Nouveau driver.

Additional testing of Kubuntu Cosmic RC on slightly newer hardware (Dell Vostro 1720 laptop, 9600M GS) with the 340.107 driver works fine.?! So issue seems specific to the to the 8600M.

I scanned the xorg and system logs, but I did not see anything obvious.
nvidia-bug-report.log.gz (113 KB)

Looks like some timing problem, when the needed module nvidia-drm is initialized, the Xserver has already failed. See if you can work around it when you add it to /etc/modules and run sudo update-initramfs -u afterwards.

In the process of troubleshooting, I was trying different drivers and ppa’s and got to the point where

sudo apt purge nvidia*

followed by:

sudo apt install nvidia-340

no longer would start the nvidia driver even using the startx option.

After reformatting and re-installing, the driver is now working correctly.??!! I have 2 of these older laptops used for Linux release testing, so if the issue happens again, I will try the above suggestion.

Thanks for your help.