This is a new post to an existing problem [My original forum post](https://askubuntu.com/questions/1118418/cant-get-nvidia-drivers-working-on-bionic-18-04).
I didn't get any answers to the original post but I've now made some important discoveries that I think will help pinpoint what the problem is here.

To recap, the original issue is with an external monitor not being detected on a new install of Ubuntu (18.04) on a W530 Thinkpad with NVIDIA Quadro K1000M card installed. Various NVIDIA drivers have been installed and tried, none of which solved the problem.

I've now summarised my findings as follows.

* When external monitor is attached, the login screen appears on the monitor and the laptop screen is blank.
* The default setting for login is **Ubuntu on Wayland**. Switching this to **Ubuntu on default**, then entering password simply causes the same login screen to reappear.
* Leaving the setting as Ubuntu on Wayland, and typing password on the monitor screen results in the desktop then appearing on the laptop screen and the monitor to go blank.
* Modifying **etc/gdm3/custom.conf** and uncommenting the line  

WaylandEnable=false
appears to make no difference to the behaviour just described.
* Running **ps -ef | grep X** shows **/usr/bin/Xwayland** process running, but no X server processes (as I was used to seeing them).
* Dropping out of the desktop and back into command mode (by typing Ctl-Alt-PF1) and logging in as non-root user, I then type **sudo startx** and the desktop appears on the external monitor – the laptop screen goes blank.
* The desktop session is now running with the root user logged in.
* Issuing command **ps -ef | grep X** shows 2 X server processes now running, 
1 - **xinit** and 
2 – **usr/lib/xorg/Xorg**
* Also, the NVIDIA X Server Settings application now appears ‘fully populated’ as shown in the attached image [NVIDIA X Server Settings under root](https://i.stack.imgur.com/FUI1T.png).
Contrast this with the same app running under the normal desktop session [NVIDIA X Server Settings when X not running](https://i.stack.imgur.com/xu929.png) .
* Furthermore, I can successfully launch applications that require hardware/graphics acceleration from this session.

So far, I’ve reached the following conclusions

1. Wayland is enabled, not X
2. If Wayland is not enabled (i.e. Ubuntu set to default on login screen), login is unsuccessful
3. The NVIDIA card and/or drivers are NOT playing nicely wth Wayland, BUT do play nicely with X when it is enabled

So, does anyone know how I can fix this awful mess so that I can get on and use my Ubuntu 18.04 to do some real work? I really don't care about the merits of Wayland vs. X...I just want to get my computer back up and running like it was before I upgraded - at a minimum, that means 

1. Being able to use an external monitor, not possible in my current environment.
2. Being able to use applications (like Sketchup under vmware) that require the accelerated hardware capability, currently missing in my default environment.

Thanks for any help.

@steeldriver you were on the money. My ~/.Xauthority file was incorrectly owned by root. Rectifying the file ownership has now allowed the non-Wayland login to proceed and display the desktop on my external monitor.

While this is a huge improvement, I am now left with the laptop screen not working. By that I mean it is blank. I tried 

1. unplugging the monitor to see if the display 'switched' back to the builtin screen, but it didn't
2. Booting up with monitor unplugged, but the laptop screen remained blank
3. Switching login to Wayland allows the laptop screen to work, but reintroduces the original problem of the external monitor not working

Any ideas on what might be causing the builtin screen not to work?