Hi all;
I tested Windows vm in LXC on Ubuntu 18.04 and its worked.
Note: remmina (for slice) or virt-viewer can connect vga.
apt install -yqq remmina-plugin-spice virt-viewer
snap install distrobuilder --classic --edge
apt install -y libguestfs-tools wimtools
distrobuilder repack-windows /home/muslu/win10.iso /home/muslu/win10_distrobuilder.iso
lxc init win10 --empty --vm -c security.secureboot=false
lxc config device override win10 root size=50GiB
lxc config device add win10 iso disk source=/home/muslu/win10_distrobuilder.iso boot.priority=10
lxc start win10 --console=vga
If install virt-viewer than vga windows will be open automaticly after lxc start.