got substituting to work along with remote building

modules/builders.nix

@@ -16,6 +16,9 @@
             keep-derivations = false;
             builders-use-substitutes = true;
             max-jobs = 0;
+            substituters = ["ssh-ng://nix-ssh@gerg-desktop" "https://cache.nixos.org/"];
+            trusted-public-keys = ["gerg-desktop:6p1+h6jQnb1MOt3ra3PlQpfgEEF4zRrQWiEuAqcjBj8=" "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="];
+            secret-key-files = "/persist/cache-keys/cache-priv-key.pem";
           };
           distributedBuilds = true;
           buildMachines = [
@@ -39,26 +42,42 @@
         };
       }
     )
-    (lib.mkIf config.localModules.remoteBuild.isBuilder {
+
+    (
+      let
+        keys = [
+          "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIq9YTf4jlVCKBKn44m4yJvj94C7pTOyaa4VjZFohNqD root@mom-laptop"
+          "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJUKHZasYQUAmRBiqtx1drDxfq18/N4rKydCtPHx461I root@game-laptop"
+        ];
+      in
+        lib.mkIf
+        config.localModules.remoteBuild.isBuilder
+        {
           users = {
             groups.builder = {};
             users.builder = {
               createHome = false;
               isSystemUser = true;
-          openssh.authorizedKeys.keys = [
+              openssh.authorizedKeys = {inherit keys;};
-            "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIq9YTf4jlVCKBKn44m4yJvj94C7pTOyaa4VjZFohNqD root@mom-laptop"
-            "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJUKHZasYQUAmRBiqtx1drDxfq18/N4rKydCtPHx461I root@game-laptop"
-          ];
               useDefaultShell = true;
               group = "builder";
             };
           };
 
-      nix.settings = {
+          nix = {
-        trusted-users = ["builder"];
+            settings = {
+              trusted-users = ["builder" "nix-ssh"];
               keep-outputs = true;
               keep-derivations = true;
             };
-    })
+            sshServe = {
+              enable = true;
+              write = true;
+              inherit keys;
+              protocol = "ssh-ng";
+            };
+          };
+        }
+    )
   ];
 }

systems/moms-laptop/default.nix

@@ -74,4 +74,11 @@
   ];
 
   system.stateVersion = "23.05";
+
+  swapDevices = [
+    {
+      device = "/swapfile";
+      size = 8 * 1024;
+    }
+  ];
 }