If you don’t need any of the functionality provided by the Twig templating engine, you can use a plain HTML file for your custom component. This is useful for developers unfamiliar with Drupal or Twig, who would prefer to use HTML in order to attach markup or various JavaScript based features (using React, for example).
The HTML file will be rendered inside the default Twig template provided by the Site Studio module. The markup will be placed inside the custom component `<div>` and after the dropzone’s `<template>`. To add HTML, add an `html` property to the YAML file and specify the path to the HTML file.

HTML file cannot be used in conjunction with the template property.

HTML file