How to use Ubuntu 18.04 on VNC without display attached?

https://launchpad.net/ubuntu/bionic/+source/xserver-xorg-video-dummy

sudo apt-get install xserver-xorg-video-dummy

How to use: Add Fake Display when No Monitor is Plugged In

This is how I solved it: I've created the virtual display using the answer to this question: https://unix.stackexchange.com/questions/378373/add-virtual-output-to-xorg

Create a 20-intel.conf file:

sudo vi /usr/share/X11/xorg.conf.d/20-intel.conf

Add the following configuration information into the file:

Section "Device"
    Identifier "intelgpu0"
    Driver "intel"
    Option "VirtualHeads" "2"
EndSection

This tells the Intel GPU to create 2 virtual displays. You can change the number of VirtualHeads to your needs.

Then I made a shell script (don't forget to set executable) and put that in Startup Applications:

#! /bin/bash

/usr/bin/xrandr -d :0 --output VIRTUAL1 --primary --auto
/usr/bin/xrandr --newmode "1600x900_60.00" 118.25 1600 1696 1856 2112 900$
/usr/bin/xrandr --addmode VIRTUAL1 "1600x900_60.00"
/usr/bin/xrandr

That way, VIRTUAL1 is set as output and connected. At boot, a new mode (found using "cvt 1600 900") is being created and appointed to VIRTUAL1.

Only issue with this is: dock is missing at reboot... Haven't solved that yet.

I tried all the suggestions to use a dummy script. It worked but only if i NEVER wanted to use a monitor attached directly to my PC. If you want remote desktop, as well as the option of a real monitor, the only solution I could find was an HDMI Pass-Through EDID Emulator. I plugged it in and everything worked seamlessly. About $20 from amazon: https://smile.amazon.com/gp/product/B07C8BHPD6/