First Try

modules/shared/default.nix

@@ -0,0 +1,29 @@
+{ config, pkgs, ... }:
+
+let
+  emacsOverlaySha256 = "06413w510jmld20i4lik9b36cfafm501864yq8k4vxl5r4hn0j0h";
+in
+{
+
+  nixpkgs = {
+    config = {
+      allowUnfree = true;
+      allowBroken = true;
+      allowInsecure = false;
+      allowUnsupportedSystem = true;
+    };
+
+    overlays =
+      # Apply each overlay found in the /overlays directory
+      let path = ../../overlays; in with builtins;
+      map (n: import (path + ("/" + n)))
+          (filter (n: match ".*\\.nix" n != null ||
+                      pathExists (path + ("/" + n + "/default.nix")))
+                  (attrNames (readDir path)))
+
+      ++ [(import (builtins.fetchTarball {
+               url = "https://github.com/dustinlyons/emacs-overlay/archive/refs/heads/master.tar.gz";
+               sha256 = emacsOverlaySha256;
+           }))];
+  };
+}