How to run an XFCE Desktop GUI on a headless Proxmox Ubuntu 20.04 Container through RDP. Trying out Snap Denarius QT as an example.
Taken from https://www.reddit.com/r/Proxmox/comments/hzg2vr/how_to_create_a_template_for_lxc_ubuntu_desktop/
sudo apt install xfce4 xfce4-goodies xorg dbus-x11 x11-xserver-utils
Select lightdm when asked which desktop.
sudo apt install xrdp
update-alternatives --set x-session-manager /usr/bin/xfce4-session
Now use Remote Desktop to RDP into the IP address. Easy enough, now you can lock it down if doing something outside of trying to set this up.