Working nix-darwin config from this Mac

pkg-installs.nix

@@ -0,0 +1,33 @@
+{ pkgs, lib, ... }:
+
+let
+  # Add one entry per program you want to install from a .pkg file
+  pkgInstalls = [
+    {
+      name = "cupsadmin";
+      url = "https://github.com/kfattic/cupsadmin/releases/download/v1.4.1/cupsadmin-1.4.1.pkg";
+      hash = "sha256-DyIyDYSjAlcU7ivyfldMapIZw5nczEBXfnLicnK6k7Y=";
+    }
+  ];
+
+  installScript = p:
+    let
+      src = pkgs.fetchurl { inherit (p) url hash; };
+    in ''
+      stamp="/usr/local/share/nix-pkg-stamps/${p.name}"
+      want="${src}"
+      if [ "$(cat "$stamp" 2>/dev/null)" != "$want" ]; then
+        echo "installing ${p.name}..."
+        if /usr/sbin/installer -pkg "$want" -target /; then
+          mkdir -p /usr/local/share/nix-pkg-stamps
+          echo "$want" > "$stamp"
+        else
+          echo "${p.name} install failed, skipping"
+        fi
+      fi
+    '';
+in
+{
+  system.activationScripts.postActivation.text =
+    lib.concatMapStringsSep "\n" installScript pkgInstalls;
+}