Same issue I have faced in a past project. Need to include the React and ReactDOM libraries in your HTML. Your compiled code, which uses React.createElement and createRoot, can't work without them.

1. React: The core library that handles the components and their logic.

2. ReactDOM: The library that renders your components onto the web page.

   ref Link:

   1. https://legacy.reactjs.org/docs/cdn-links.html (Add these two <script> tags to your main-layout.hbs file.)

   2. https://react.dev/learn/add-react-to-an-existing-project