RealVNC viewer returns grayed screen with raspberry Pi5 realVNC server

Hi,

I have a Raspberry Pi5 with RealVNC server installed and active.

It works great with the default Raspberry default desktop, but I dislike it and therefore I tested all different desktop environment available and compatible with it.

Whatever DE runs on Raspberry Pi, RealVNC viewer returns a grayed screen.

So I tried to modify the xstartup file as written here: https://help.realvnc.com/hc/en-us/articles/360003474792-Why-does-RealVNC-Server-in-Virtual-Mode-on-Linux-appear-to-hang-show-a-gray-screen-or-not-start-at-all#custom-xstartup-files-0-1 

But nothing works.

So I would like to understand what is missing so I could use my preferred DE plasma on my Raspberry Pi5 and control it remotely from my Windows laptop.

thx