Ubuntu 18.04 stopped working with NVIDIA drivers

You might need to have Direct Rendering Manager Kernel Mode Setting enabled on system boot.
NVIDIA driver's PRIME Synchronization support relies on DRM-KMS, which is disabled by default.
Find more comprehensive information in the discussion on the NVIDIA GPU Unix Graphics forum.

Execute sudo nano /etc/default/grub and add the parameter nvidia-drm.modeset=1 to the line GRUB_CMDLINE_LINUX_DEFAULT. Save the change you've made and run sudo update-grub.
Restart the Ubuntu operating system, and now everything should work properly, right as expected.

I was able to get it working with the latest Nvidia-418 drivers on a Lenovo W530 with the Nvidia GK107GLM Quadro K2000M:

1. Edit the sudo nano /etc/default/grub and remove "quiet splash" from GRUB_CMDLINE_LINUX_DEFAULT and then sudo update-grub (that may be similar then adding nvidia-drm.modeset=1)
2. Switch to LightDM: sudo dpkg-reconfigure lightdm (necessary so my second monitor was recognized)
3. Install PPA with latest drivers: sudo add-apt-repository ppa:graphics-drivers/ppa and sudo apt-get update
4. Install latest recommended driver (in my case Nvidia 418): sudo ubuntu-drivers autoinstall