La salida del complemento Rollup “rollup-plugin-polyfills-loader” da un error.

Tengo el siguiente rollup.config.js (solo he pegado la información relevante para este problema):

import html from '@web/rollup-plugin-html';
import polyfillsLoader from '@web/rollup-plugin-polyfills-loader';
const htmlPlugin = html({
  inputPath: 'index.html',
  inject: false,
});
polyfillsLoader({
  modernOutput: {
    name: 'modern',
  },
  // Detección de características para cargar paquetes antiguos
  legacyOutput: {name: 'legacy', test: '!(\'noModule\' in HTMLScriptElement.prototype)'},

  // Lista de polyfills a inyectar (cada uno tiene detección de características individual)
  polyfills: {
    hash: true,
    coreJs: true,
    regeneratorRuntime: true,
    fetch: true,
    webcomponents: true,
    // Configuración personalizada para cargar el módulo de soporte de polyfill de Lit,
    // necesario para el interfaz con los polyfills de webcomponents
    custom: [
      {
        name: 'lit-polyfill-support',
        path: 'node_modules/lit/polyfill-support.js',
        test: '!(\'attachShadow\' in Element.prototype)',
        module: false,
      },
    ],
  },
}),

Esto en realidad inyecta el siguiente script en mi construcción:

<script>(function () {
  function polyfillsLoader() {
    function loadScript(src, type, attributes = []) {
      return new Promise(function (resolve) {
        var script = document.createElement('script');

        function onLoaded() {
          if (script.parentElement) {
            script.parentElement.removeChild(script);
          }

          resolve();
        }

        script.src = src;
        script.onload = onLoaded;
        attributes.forEach(att => {
          script.setAttribute(att.name, att.value);
        });

        script.onerror = function () {
          console.error('[polyfills-loader] failed to load: ' + src + ' check the network tab for HTTP status.');
          onLoaded();
        };

        if (type) script.type = type;
        document.head.appendChild(script);
      });
    }

    var polyfills = [];

    if (!('noModule' in HTMLScriptElement.prototype)) {
      polyfills.push(loadScript('./polyfills/regenerator-runtime.de2e6a3a74a500cae72a3cab1a403efc.js'));
    }

    if (!('fetch' in window)) {
      polyfills.push(loadScript('./polyfills/fetch.a1ad5fb96dc0cb61b9454244c9bd7fe6.js'));
    }

    if (!('attachShadow' in Element.prototype) || !('getRootNode' in Element.prototype) || window.ShadyDOM && window.ShadyDOM.force) {
      polyfills.push(loadScript('./polyfills/webcomponents.d7ffce1754011cfedff5f846f12e0c11.js'));
    }

    if (!('noModule' in HTMLScriptElement.prototype) && 'getRootNode' in Element.prototype) {
      polyfills.push(loadScript('./polyfills/custom-elements-es5-adapter.3342b468203af1a14ca005e80d14148f.js'));
    }

    if (!('attachShadow' in Element.prototype)) {
      polyfills.push(loadScript('./polyfills/lit-polyfill-support.82aa27f27be323af5a455ac87919622a.js'));
    }

    function loadFiles() {
      if (!('noModule' in HTMLScriptElement.prototype)) {
        [function () {
          return loadScript('./legacy-my-header-d84233c1.js', 'module', []);
        }, function () {
          return loadScript('./legacy-my-footer-353e3024.js', 'module', []);
        }, function () {
          return loadScript('./legacy-my-breadcrumbs-6977da2c.js', 'module', []);
        }, function () {
          return loadScript('./legacy-my-anchor-menu-3a71e855.js', 'module', []);
        }, function () {
          return loadScript('./legacy-my-contact-box-605983a9.js', 'module', []);
        }, function () {
          return loadScript('./legacy-my-transition-96158dc5.js', 'module', []);
        }, function () {
          return loadScript('./legacy-my-animated-slot-d7901404.js', 'module', []);
        }].reduce(function (a, c) {
          return a.then(c);
        }, Promise.resolve());
      } else {
        [function () {
          return loadScript('./my-header-df4bd84c.js', 'module', []);
        }, function () {
          return loadScript('./my-footer-2e03a59d.js', 'module', []);
        }, function () {
          return loadScript('./my-breadcrumbs-ebb2c4c1.js', 'module', []);
        }, function () {
          return loadScript('./my-anchor-menu-9f6da4d8.js', 'module', []);
        }, function () {
          return loadScript('./my-contact-box-77b64be7.js', 'module', []);
        }, function () {
          return loadScript('./my-transition-b8f34c3f.js', 'module', []);
        }, function () {
          return loadScript('./my-animated-slot-7cfd347d.js', 'module', []);
        }].reduce(function (a, c) {
          return a.then(c);
        }, Promise.resolve());
      }
    }

    if (polyfills.length) {
      Promise.all(polyfills).then(loadFiles);
    } else {
      loadFiles();
    }
  }

  if (!('noModule' in HTMLScriptElement.prototype)) {
    var s = document.createElement('script');

    function onLoaded() {
      document.head.removeChild(s);
      polyfillsLoader();
    }

    s.src = "./polyfills/core-js.26813355b620c9d0fe88992b4621ff45.js";
    s.onload = onLoaded;

    s.onerror = function () {
      console.error('[polyfills-loader] failed to load: ' + s.src + ' check the network tab for HTTP status.');
      onLoaded();
    };

    document.head.appendChild(s);
  } else {
    polyfillsLoader();
  }
})();</script>

Esto me da un error:

Se esperaba ‘)’

¿Qué he hecho mal?