Instll steam and the zfs_clone_send / zfs_clone_recv scripts.

nix/configuration/util/unfree_polyfill/default.nix

@@ -0,0 +1,15 @@
+{ config, lib, ... }:
+
+let
+  inherit (builtins) elem;
+  inherit (lib) getName mkOption;
+  inherit (lib.types) listOf str;
+in
+{
+  # Pending https://github.com/NixOS/nixpkgs/issues/55674
+  options.allowedUnfree = mkOption {
+    type = listOf str;
+    default = [ ];
+  };
+  config.nixpkgs.config.allowUnfreePredicate = p: elem (getName p) config.allowedUnfree;
+}