A sddm theme that looks like xdm
Just copy everything to your sddm themes directory (usually /usr/share/sddm/themes/xdm ) and set the theme to xdm in your sddm.conf
Add the following to your nixos config.
# Enable plasma and sddm
services.xserver = {
enable = true;
desktopManager.plasma5.enable = true;
displayManager.sddm.enable = true;
}
# Enable this theme
services.xserver.displayManager.sddm.theme = "xdm";
environment.systemPackages = [ pkgs.sddm-xdm-theme ];
There are options to disable animations and to set the background and the logo image in theme.conf.
The xorg image is taken from the xdm git https://github.com/freedesktop/xorg-xdm/blob/master/config/xorg.xpm