Comment 77 for bug 1705369

I had the blank screen, no login screen problem.

The computer was otherwise running though.

I ssh-ed from another computer to the problem computer
to execute the suggested commands.

If on a home network you can login to your router with a
web browser to get the IP address for your problem computer.

Mine was 192.168.1.3

The following fixed the problem for me.

First I did (without the comment).

  sudo apt-get install lightdm # This showed lightdm was installed

Second I did uname -r and found the completion for
the linux-headers-$(uname -r) command.

I don't know why I didn't use the suggested:
    sudo apt install linux-headers-$(uname -r)

Then I did the suggested commands, one after the other:
  sudo apt purge gdm3
  sudo apt purge nvidia*
  sudo apt install linux-headers-4.13.0-16-generic # ADJUST THIS
  sudo apt install nvidia-384
  sudo dpkg-reconfigure lightdm # Suggested when 1st command ran
  sudo shutdown -r now # Restart

Went to the problem computer, the login screen came up.

The Desktop Environment that was selected was:
  Ubuntu on Xorg(Default)

I was able to login.

My problem computer is at least 10 years old.