Are you possibly lacking a remote desktop protocol?
It is not referenced anywhere (at least can’t find any mention), but it seems that running lxc console <vm name> --type=vga does imply that some SPICE server is running:
To start the VGA console with graphical output for your VM, you must install a SPICE client (for example, virt-viewer or spice-gtk-client ).
Thanks for the information! I may end up going that route. What I was trying to attempt though is using the HDMI output from the host where the LXC is running. The monitor would then display the NixOS’ LXC’s desktop environment, KDE in my case.
You may investigate a different solution if e.g you would need “performance” from the desktop environment. Maybe re-route the desktop instance video output to the host HDMI?
I got an environment with KDE, using Remmina, can also span on multiple monitors (got 3), no issue! - beware of possible wayland and x11 shenanigans