How to Create Virtual Display, When No Screen Is Connected? (X11Vnc)

For an installation I need to have access to the current running screen on a Ubuntu 20 machine. I want to be able to remotely access it, which I got to work using x11vnc. But I also want to be able to connect a screen locally, when needed.

Currently if no display is connected the VNC stream is black. When using xserver-xorg-video-dummy it works, but the local screen does not get recognized anymore. Is there a way to have both running?

I feel like the -create option in x11vnc should do what I am looking for, but I can not get it to work. Here's a snippet from the manual: -create

-create

First try to find the user's display using FINDDISPLAY, if that doesn't succeed create an X session via the FINDCREATEDISPLAY method. This is an alias for "-display WAIT:cmd=FINDCREATEDISPLAY-Xvfb".