debian 11 x11vnc not working

[kx3210]

I have tried to get x11vnc working on a vanilla debian 11 install. It works on mint no problem but not on debian. output is

14/12/2021 20:48:04 passing arg to libvncserver: -rfbauth
14/12/2021 20:48:04 passing arg to libvncserver: /etc/x11vnc/vncpwd
14/12/2021 20:48:04 passing arg to libvncserver: -rfbport
14/12/2021 20:48:04 passing arg to libvncserver: 5900
14/12/2021 20:48:04 x11vnc version: 0.9.16 lastmod: 2019-01-05 pid: 4530
14/12/2021 20:48:04 XOpenDisplay(":0") failed.
14/12/2021 20:48:04 Trying again with XAUTHLOCALHOSTNAME=localhost ...

14/12/2021 20:48:04 ***************************************
14/12/2021 20:48:04 *** XOpenDisplay failed (:0)

Service file
Unit]
Description=Start x11vnc
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/x11vnc -display :0 -auth /run/user/1000/gdm/xauthority -forever -noxdamage -repeat -rfbauth /etc/x11vnc/vncpwd -rfbport 5900 -shared -o /var/log/x11vnc.log

[Install]
WantedBy=multi-user.target

The service file works on mint with no problem why not debian ?

[kx3210]

Noticed in the logs that there were some errors in the GDM installation. So started again and used LightDM and installed x11vnc exactly as before and it works without a problem. This was a vanilla installation nothing else but x11vnc installed.

[dilberts_left_nut]

What is a vanilla installation?
Gnome/Wayland?

Seems a bad choice if you want to use x11vnc.

[kx3210]

Vanilla installation just debian nothing else installed. Used the graphic installation so not a lot of choices for the installation - did add cinnamon
Gnome/Wayland - don't understand the question. Only difference between the 2 installs was changing from GDM to LightDM.
It is running X11 XDG_SESSION_TYPE=x11. and cinnamon 4.8.6 as below

OS: Debian 11 bullseye
Kernel: x86_64 Linux 5.10.0-9-amd64
Uptime: 17m
Packages: 2090
Shell: bash 5.1.4
Resolution: 1600x900
DE: Cinnamon 4.8.6
WM: Muffin
WM Theme: (Default)
GTK Theme: Adwaita [GTK2/3]
Icon Theme: gnome
Font: Sans 9
Disk: 1.1T / 8.0T (13%)
CPU: Intel Core i5-2500K @ 4x 3.7GHz [30.0°C]
GPU: Mesa DRI Intel(R) HD Graphics 3000 (SNB GT2)
RAM: 1445MiB / 15925MiB

Why is Debian a bad choice for using x11vnc ?