How can I embed a webform in an Ionic React app?
Here is specifically how to do this in Ionic + React.
First, Webform share uses the iframe-resizer library, which has an official react component.
So install the library into your app:
npm install iframe-resizer-react
Then add a component such as WebformContact.tsx (this example uses TypeScript):
import * as React from 'react';
import {
  IonContent, IonPage,
} from '@ionic/react';
import IframeResizer from 'iframe-resizer-react';

const styleWebformIframeEmbed: React.CSSProperties = {
  width: '1px',
  minWidth: '100%',
};

const WebformContact = () =&gt; (
  &lt;IonPage&gt;
    &lt;IonContent&gt;
      &lt;IframeResizer
        src=&quot;https://example.com/webform/MY-WEBFORM-MACHINENAME/share/iframe-resizer/4.2.10&quot;
        title=&quot;MY WEBFORM TITLE&quot;
        frameBorder=&quot;0&quot;
        allowFullScreen
        style={styleWebformIframeEmbed}
      /&gt;
    &lt;/IonContent&gt;
  &lt;/IonPage&gt;
);
export default WebformContact;

Note that you need to install the same version of iframe-resizer in both webform (drupal) + your ionic app.
Also note that if your site is https, you should be sure to specify that in the src tag; when React is hosted by Ionic, it will be run from http://localhost (Android) or http://capacitor (iOS), so if you do not specify https for the server, you will get a difficult to understand error:

iframeResizer.js:822 Failed to execute 'postMessage' on 'DOMWindow':
The target origin provided

But really what this means is that you are trying to access an https server in an iframe with http.  So specify https!