Newer nVidia drivers 390.77 can't detect external display on Lenovo ThinkPad

[the-spyke]

After recent update of nVidia drivers to 390.77 on Ubuntu 18.04 my external display stopped working. Is there some way to fix it (check X config/etc.) or at least to rollback to previous minor version of drivers (was 390.66 or something similar)? xrandr shows only internal screen.

Lenovo ThinkPad P50, nVidia Quadro M1000M
Ubuntu 18.04 (4.15.0-36-generic), nvidia 390.77

[Autodave]

If you go into Settings -> Additional Drivers you should be able to choose from several drivers.

[the-spyke]

I see only two: nvidia 390.77 tested and nouveau. If I try to apt install nvidia-384 or 375 it still installs 390.

[Autodave]

I apologize for giving you bad info: they used to always be listed there. Evidently, as I just found out for myself, they are no longer listed. Maybe someone else will be able to help out here.

[the-spyke]

No problem. I Nvidia's bug report I see:

ERROR: Kernel configuration is invalid."
include/generated/autoconf.h or include/config/auto.conf are missing."
Run 'make oldconfig && make prepare' on kernel src to fix it."

Is it safe to run those commands? Where I should run them? Thanks

[the-spyke]

Disabling NVIDIA KMS (enabled by default in 390.77) resolves the issue:
Edit /lib/modprobe.d/nvidia-kms.conf file and set modeset to 0:
options nvidia-drm modeset=0

Save, update initramfs and reboot:
sudo update-initramfs -u
reboot