async function polyfill() {
  const { hydrateShadowRoots } = await import('@webcomponents/template-shadowroot/template-shadowroot.js');
  hydrateShadowRoots(document.body);
}

if(!(new DOMParser().parseFromString(`<p><template shadowroot="open"></template></p>`, 'text/html', {
  includeShadowRoots: true
}).querySelector('p')?.shadowRoot))
  polyfill();