Yes the fetcher seems to work

Try this

{
  lib,
  stdenv,
  nodejs,
  fetchFromGitHub,
  yarn-berry_3,
}:
let
  yarn-berry = yarn-berry_3;
in

stdenv.mkDerivation (finalAttrs: rec {
  pname = "verdaccio";
  version = "6.1.2";

  src = fetchFromGitHub {
    owner = "verdaccio";
    repo = pname;
    rev = "v${version}";
    hash = "sha256-EssvN5HtGI5Hmw4EXetj5nzrkBZAAJGgOx09dlYJzhI=";
  };

  nativeBuildInputs = [
    nodejs
    yarn-berry
    yarn-berry.yarnBerryConfigHook
  ];

  offlineCache = yarn-berry.fetchYarnBerryDeps {
    inherit (finalAttrs) src;
    hash = "sha256-jzkmDxQtIFMa1LIPcvKKsXIItPntgXTavoWhd5eZWyQ=";
  };

  buildPhase = ''
    runHook preBuild
    yarn run build
    runHook postBuild
  '';

  installPhase = ''
    runHook preInstall

    mkdir -p $out

    cp -r {bin,build,package.json,.pnp.cjs} $out/

    runHook postInstall
  '';

  meta = with lib; {
    description = "A simple, zero-config-required local private npm registry";
    longDescription = ''
      Verdaccio is a simple, zero-config-required local private npm registry. No need for an entire database just to get started! Verdaccio comes out of the box with its own tiny database, and the ability to proxy other registries (eg. npmjs.org), caching the downloaded modules along the way. For those looking to extend their storage capabilities, Verdaccio supports various community-made plugins to hook into services such as Amazon's s3, Google Cloud Storage or create your own plugin.
    '';
    homepage = "https://verdaccio.org";
    license = licenses.mit;
  };
})

Yes the fetcher seems to work but when you try to run the entrypoint script it doesn't work

Try this

{
  lib,
  stdenv,
  nodejs,
  fetchFromGitHub,
  yarn-berry_3,
}:
let
  yarn-berry = yarn-berry_3;
in

stdenv.mkDerivation (finalAttrs: rec {
  pname = "verdaccio";
  version = "6.1.2";

  src = fetchFromGitHub {
    owner = "verdaccio";
    repo = pname;
    rev = "v${version}";
    hash = "sha256-EssvN5HtGI5Hmw4EXetj5nzrkBZAAJGgOx09dlYJzhI=";
  };

  nativeBuildInputs = [
    nodejs
    yarn-berry
    yarn-berry.yarnBerryConfigHook
  ];

  offlineCache = yarn-berry.fetchYarnBerryDeps {
    inherit (finalAttrs) src;
    hash = "sha256-jzkmDxQtIFMa1LIPcvKKsXIItPntgXTavoWhd5eZWyQ=";
  };

  buildPhase = ''
    runHook preBuild
    yarn run build
    runHook postBuild
  '';

  installPhase = ''
    runHook preInstall

    mkdir -p $out

    cp -r {bin,build,package.json,.pnp.cjs} $out/

    runHook postInstall
  '';

  meta = with lib; {
    description = "A simple, zero-config-required local private npm registry";
    longDescription = ''
      Verdaccio is a simple, zero-config-required local private npm registry. No need for an entire database just to get started! Verdaccio comes out of the box with its own tiny database, and the ability to proxy other registries (eg. npmjs.org), caching the downloaded modules along the way. For those looking to extend their storage capabilities, Verdaccio supports various community-made plugins to hook into services such as Amazon's s3, Google Cloud Storage or create your own plugin.
    '';
    homepage = "https://verdaccio.org";
    license = licenses.mit;
  };
})

Yes the fetcher seems to work but when you try to run the entrypoint script it doesn't work

Try this

{
  lib,
  stdenv,
  nodejs,
  fetchFromGitHub,
  yarn-berry_3,
}:
let
  yarn-berry = yarn-berry_3;
in

stdenv.mkDerivation (finalAttrs: rec {
  pname = "verdaccio";
  version = "6.1.2";

  src = fetchFromGitHub {
    owner = "verdaccio";
    repo = pname;
    rev = "v${version}";
    hash = "sha256-EssvN5HtGI5Hmw4EXetj5nzrkBZAAJGgOx09dlYJzhI=";
  };

  nativeBuildInputs = [
    nodejs
    yarn-berry
    yarn-berry.yarnBerryConfigHook
  ];

  offlineCache = yarn-berry.fetchYarnBerryDeps {
    inherit (finalAttrs) src;
    hash = "sha256-jzkmDxQtIFMa1LIPcvKKsXIItPntgXTavoWhd5eZWyQ=";
  };

  buildPhase = ''
    runHook preBuild
    yarn run build
    runHook postBuild
  '';

  installPhase = ''
    runHook preInstall

    mkdir -p $out

    cp -r {bin,build,package.json,.pnp.cjs} $out/

    runHook postInstall
  '';

  meta = with lib; {
    description = "A simple, zero-config-required local private npm registry";
    longDescription = ''
      Verdaccio is a simple, zero-config-required local private npm registry. No need for an entire database just to get started! Verdaccio comes out of the box with its own tiny database, and the ability to proxy other registries (eg. npmjs.org), caching the downloaded modules along the way. For those looking to extend their storage capabilities, Verdaccio supports various community-made plugins to hook into services such as Amazon's s3, Google Cloud Storage or create your own plugin.
    '';
    homepage = "https://verdaccio.org";
    license = licenses.mit;
  };
})

and run ./result/bin/verdaccio

Yes I think that perhaps it should be wiser to package it for pnpm for now and use the unstable versioning till 7.x is released.

Meanwhile I will raise the topic about pnp

Dunno...

  buildPackages' = buildPackages.extend (self: super: {nodejs = nodejs_23;});
  buildNpmPackage23 = buildNpmPackage.override {
    buildPackages = buildPackages';
  };

Ended up with something like this and this seemed to work. There are probably better ways to do this 🤷