Now it should work?

default.nix

@@ -1,13 +1,21 @@
-(import
-  (
-    let
-      lock = builtins.fromJSON (builtins.readFile ./flake.lock);
-      nodeName = lock.nodes.root.inputs.flake-compat;
-    in
-    fetchTarball {
-      url = lock.nodes.${nodeName}.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.${nodeName}.locked.rev}.tar.gz";
-      sha256 = lock.nodes.${nodeName}.locked.narHash;
-    }
-  )
-  { src = ./.; }
-).defaultNix
+{ pkgs ? null, fenix ? null }: (args: let
+  pkgs = if (builtins.tryEval args.pkgs).success && args.pkgs != null
+    then args.pkgs
+    else import (import ./flake-compat.nix).inputs.nixpkgs { };
+  fenix = if (builtins.tryEval args.fenix).success && args.fenix != null
+    then args.fenix
+    else import (import ./flake-compat.nix).inputs.fenix { };
+in rec {
+  # The `lib`, `modules`, and `overlays` names are special
+  lib = import ./lib { inherit pkgs; }; # functions
+  modules = import ./modules; # NixOS modules
+  overlays = import ./overlays; # nixpkgs overlays
+
+  auditok = pkgs.callPackage ./pkgs/auditok { };
+  bip39 = pkgs.callPackage ./pkgs/bip39 { };
+  ffsubsync = pkgs.callPackage ./pkgs/ffsubsync { inherit auditok pysubs2; };
+  my-bookmarks-pl = pkgs.callPackage ./pkgs/my-bookmarks-pl { };
+  neocities-deploy = pkgs.callPackage ./pkgs/neocities-deploy { inherit fenix; };
+  pysubs2 = pkgs.callPackage ./pkgs/pysubs2 { };
+  subtitlecomposer = pkgs.callPackage ./pkgs/subtitlecomposer { };
+}) { inherit pkgs fenix; }

flake-compat.nix

@@ -0,0 +1,13 @@
+(import
+  (
+    let
+      lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+      nodeName = lock.nodes.root.inputs.flake-compat;
+    in
+    fetchTarball {
+      url = lock.nodes.${nodeName}.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.${nodeName}.locked.rev}.tar.gz";
+      sha256 = lock.nodes.${nodeName}.locked.narHash;
+    }
+  )
+  { src = ./.; }
+).defaultNix

flake.nix

@@ -3,6 +3,8 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     flake-compat.url = "https://flakehub.com/f/edolstra/flake-compat/1.tar.gz";
+    fenix.url = "github:nix-community/fenix";
+    fenix.inputs.nixpkgs.follows = "nixpkgs";
   };
   outputs =
     { self
@@ -26,24 +28,10 @@
       modules = import ./modules;
 
       legacyPackages = forAllSystems (system:
-      let
-        pkgs = import nixpkgs { inherit system; };
-      in rec {
-        # The `lib`, `modules`, and `overlays` names are special
-        lib = import ./lib { inherit pkgs; }; # functions
-        modules = import ./modules; # NixOS modules
-        overlays = import ./overlays; # nixpkgs overlays
-
-        auditok = pkgs.callPackage ./pkgs/auditok { };
-        bip39 = pkgs.callPackage ./pkgs/bip39 { };
-        ffsubsync = pkgs.callPackage ./pkgs/ffsubsync { inherit auditok pysubs2; };
-        my-bookmarks-pl = pkgs.callPackage ./pkgs/my-bookmarks-pl { };
-        neocities-deploy = pkgs.callPackage ./pkgs/neocities-deploy {
+        import ./default.nix {
+          pkgs = import nixpkgs { inherit system; };
           fenix = fenix.outputs.packages.${system};
-        };
-        pysubs2 = pkgs.callPackage ./pkgs/pysubs2 { };
-        subtitlecomposer = pkgs.callPackage ./pkgs/subtitlecomposer { };
-      });
+        });
       packages = forAllSystems (system: nixpkgs.lib.filterAttrs (_: v: nixpkgs.lib.isDerivation v) self.legacyPackages.${system});
     };
 }

justfile

@@ -2,3 +2,9 @@
 format:
     just --unstable --fmt
     nix-shell -p alejandra --run "alejandra ."
+
+flake-build pkg:
+    nix build .#"{{ pkg }}"
+
+normal-build pkg:
+    nix-build . -A {{ pkg }}

pkgs/neocities-deploy/default.nix

@@ -4,7 +4,6 @@
 , fenix
 ,
 }:
-
 let
   toolchain = fenix.minimal.toolchain;
   buildRustPackage = (pkgs.makeRustPlatform {
@@ -22,12 +21,12 @@ in
     rev = "v${version}";
     hash = "sha256-Ax1xmNyt+Gymk28p9lXh+CV17rWjMBKIZtc+nthic+8=";
   };
-  cargoHash = "sha256-R6TTB+TXA44vp+7454fu9/5bscgNao0wuskdgpA2BwY=";
+  cargoHash = "sha256-wdO46fRqzrWZNSoNAA5FHBckUxLtsxmc72UVtmGhJYU=";
   doCheck = false;
   meta = with lib; {
     description = "A command-line tool for deploying your Neocities site";
     homepage = "https://github.com/kugland/neocities-deploy";
     license = licenses.gpl3;
-    maintainers = [ pkgs.maintainers.kugland ];
+    maintainers = with pkgs.maintainers; [ kugland ];
   };
 }