embedding Flow components into TypeScript views does not work

If I follow the Creating an Embedded Vaadin Application Tutorial in order to embed a server-side Vaadin component into a TypeScript Vaadin view, my application does not work as expected:

• the tutorial tells me that I need to include the webcomponents-loader script and gives code snippets how to do that. These code snippets do not work. Moreover, the entire step of loading WebComponents polyfils is not needed because all browsers supported by Vaadin 15+ do support Web Components natively.
• If I skip the WC polyfils (or if I manage to find my way to load them), embedding still fails with a Uncaught TypeError: window.Vaadin.Flow.initApplication is not a function error:

ServerCounter.java:

public class ServerCounter extends Div {

    public ServerCounter() {
        add(new Label("Server-side counter"));
    }

    public static class Exporter extends WebComponentExporter<ServerCounter> {
        public Exporter() {
            super("server-counter");
        }

        @Override
        protected void configureInstance(
                WebComponent<ServerCounter> webComponent,
                ServerCounter counter) {
        }
    }
}

index.html:

<script type="module" src="web-component/server-counter.js"></script>

main-layout.ts:

render() {
  return html`
      <server-counter></server-counter>
      <slot></slot>
  `;
}

[vlukashov]

Another use case for cross-app embedding: gradual migration from an older Vaadin app to Fusion: want to embed parts of the old app inside the new app, without putting the old and the new app into one project.

[Artur-]

A working example can be found here https://artur.app.fi/embed-fusion-flow/. Code here https://github.com/Artur-/embed-fusion-flow