fix(kratos): replace gdm with greetd/tuigreet login manager

hosts/m3-kratos/configuration.nix

@@ -14,7 +14,7 @@
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
   boot.initrd.kernelModules = ["amdgpu"];
-  boot.kernelPackages = pkgs.linuxPackages_6_18;
+  boot.kernelPackages = pkgs.linuxPackages_7_0;
   services.xserver.videoDrivers = ["amdgpu"];
   security.polkit.enable = true;
   security.pam.services.gdm.enableGnomeKeyring = true;

hosts/m3-kratos/services/default.nix

@@ -1,6 +1,7 @@
 {pkgs, ...}: {
   imports = [
     ./containers
+    ./greetd.nix
     ./mem0.nix
     # ./n8n.nix
     ./netbird.nix
@@ -29,6 +30,6 @@
         userServices = true;
       };
     };
-    displayManager.gdm.enable = true;
+    # displayManager.gdm.enable = true;
   };
 }

hosts/m3-kratos/services/greetd.nix

@@ -0,0 +1,39 @@
+# greetd login manager for m3-kratos (replaces broken GDM on nixos-unstable).
+# Uses tuigreet as the greeter, launching Hyprland after authentication.
+{
+  pkgs,
+  config,
+  ...
+}: let
+  inherit (config.programs.hyprland) package asHyprland;
+  tuigreet = "${pkgs.tuigreet}/bin/tuigreet";
+  startHyprland = "${asHyprland.package}/bin/start-hyprland";
+in {
+  services.greetd = {
+    enable = true;
+
+    settings = {
+      default_session = {
+        user = "greeter";
+        command = builtins.concatStringsSep " " [
+          tuigreet
+          "--time"
+          "--remember"
+          "--remember-session"
+          "--remember-user-session"
+          "--user-menu"
+          "--user-menu-min-uid 1000"
+          "--asterisks"
+          "--power-shutdown '${config.systemd.package}/bin/systemctl poweroff'"
+          "--power-reboot '${config.systemd.package}/bin/systemctl reboot'"
+          "--cmd ${startHyprland}"
+        ];
+      };
+    };
+  };
+
+  # Required for --remember and --remember-user-session to persist session choices.
+  systemd.tmpfiles.rules = [
+    "d /var/cache/tuigreet 0755 greeter greeter - -"
+  ];
+}