No, you can replace the distro to any that proxmox will support and that has lightdm, you just need to modify the 2nd installation script also as it uses Ubuntu packages for Kodi. The easiest it should be for apt based distributions. But actually the heavy lifting that those scripts do is around passing throughout devices especially in Unprivileged mode, which is tricky in lxc. So you could remove or even allow to fail the apt parts and install what you need manually in the container after creation.