I have used the following commands in kalilinux-rolling to use novnc

apt install lightdm
sudo apt install -y novnc x11vnc
sudo apt update && sudo apt install -y kali-desktop-kde

when i run this command `x11vnc -display :0 -autoport -localhost -nopw -bg -xkb -ncache -ncache_cr -quiet -forever`

I am getting the following error.

13/04/2022 13:51:32 ***************************************
13/04/2022 13:51:32 *** XOpenDisplay failed (:0)

*** x11vnc was unable to open the X DISPLAY: ":0", it cannot continue.
*** There may be "Xlib:" error messages above with details about the failure.

When I run this command `update-alternatives --config x-session-manager`
I get the following data

There is 1 choice for the alternative x-session-manager (providing /usr/bin/x-session-manager).

Selection Path Priority Status
* 0 /usr/bin/startplasma-x11 40 auto mode
1 /usr/bin/startplasma-x11 40 manual mode

Can anyone tell me what I am missing here