Forcing unstable does not work well with setting nix paths, separate that into its own nix file

nixos/base.nix

@@ -24,21 +24,6 @@
     };
   };
 
-  # This will add each flake input as a registry
-  # To make nix commands consistent with your flake
-  nix.registry = (lib.mapAttrs (_: flake: {inherit flake;})) ((lib.filterAttrs (_: lib.isType "flake")) inputs);
-
-  # This will additionally add your inputs to the system's legacy channels
-  # Making legacy nix commands consistent as well, awesome!
-  nix.nixPath = ["/etc/nix/path"];
-  environment.etc =
-    lib.mapAttrs'
-    (name: value: {
-      name = "nix/path/${name}";
-      value.source = value.flake;
-    })
-    config.nix.registry;
-
   # Enable flakes and garbage collection
   nix = {
     settings = {
@@ -50,8 +35,10 @@
     gc = {
       automatic = true;
       dates = "weekly";
-      options = "--delete-older-than 14d";
+      options = "--delete-older-than 1w"
     };
+    # You can also manually optimize the store via nix-store --optimise
+    settings.auto-optimise-store = true;
   };
 
   # Set timezone

nixos/desktop.nix

@@ -21,6 +21,7 @@
 
     # Modules
     ./modules/security.nix
+    ./modules/legacy.nix
 
     # Hardware
     ./hardware/machines/desktop.nix

nixos/modules/legacy.nix

@@ -0,0 +1,16 @@
+{
+  # This will add each flake input as a registry
+  # To make nix commands consistent with your flake
+  nix.registry = (lib.mapAttrs (_: flake: {inherit flake;})) ((lib.filterAttrs (_: lib.isType "flake")) inputs);
+
+  # This will additionally add your inputs to the system's legacy channels
+  # Making legacy nix commands consistent as well, awesome!
+  nix.nixPath = ["/etc/nix/path"];
+  environment.etc =
+    lib.mapAttrs'
+    (name: value: {
+      name = "nix/path/${name}";
+      value.source = value.flake;
+    })
+    config.nix.registry;
+}

nixos/server.nix

@@ -11,6 +11,7 @@
 
     # Modules
     ./modules/security.nix
+    ./modules/legacy.nix
 
     # Hardware
     ./hardware/machines/server.nix