https://gitlab.com/librephoenix/nixos-config
https://gitlab.com/librephoenix/nixos-config/-/blob/main/flake.nix?ref_type=heads

   nixpkgs-patched = (import nixpkgs { inherit system; }).applyPatches {
      name = "nixpkgs-patched";
      src = nixpkgs;
      patches = [ ./patches/emacs-no-version-check.patch ];
    };
    # configure pkgs
    pkgs = import nixpkgs-patched {
      inherit system;
      config = { allowUnfree = true; };
      overlays = [ rust-overlay.overlays.default ];
    };

    # configure lib
    lib = nixpkgs.lib;