fix

flake.nix

@@ -12,6 +12,7 @@
       packages = forAllSystems (system:
         let
           pkgs = import nixpkgs { inherit system; };
+          pythonEnv = pkgs.python3.withPackages (ps: [ ps.pillow ]);
         in
         {
           clip-thumbnailer = pkgs.stdenvNoCC.mkDerivation {
@@ -26,6 +27,8 @@
               runHook preInstall
 
               install -Dm755 ${./clip-thumbnailer.py} $out/bin/clip-thumbnailer
+              substituteInPlace $out/bin/clip-thumbnailer --replace \
+                "#!/usr/bin/env python" "#!${pythonEnv}/bin/python3"
               ln -s $out/bin/clip-thumbnailer $out/bin/clip-extract-preview
               install -Dm644 ${./clip.thumbnailer} $out/share/thumbnailers/clip.thumbnailer
               install -Dm644 ${./clip-studio.xml} $out/share/mime/packages/clip-studio.xml