Custom Unity Hub Project Template Preview Image/Video (using HTML+CSS in package description)

Steps

• Customize your project template package.json file (using 7zip in Administrator mode)
• Project templates are inside Unity editor installation folder (like: 2022_3\Editor\Data\Resources\PackageManager\ProjectTemplates\)
• Example package.json here to add video (and hide default preview image)
  https://gist.github.com/unitycoder/cc472faec83f4941d032e2010ce889ea
• Remember to close Hub completely (so that it reloads packages)
• Whats happening? This line has HTML & CSS inside description and Unity hub renders them.. The CSS is for hiding default project template thumbnail.
  "description": "Some description here.. <video width='320' height='240' autoplay style=''><source src='https://cdn.mtdv.me/video/rick.mp4' type='video/mp4'></video><style>.template-preview__image{display:none !important;}</style>",

WARNING!

• This means, if you download custom project templates from web/unknown sources, they might “call home” with custom html running on template selection.. (capture your IP address or possible more..) **I did report this to Unity Bug Bounty earlier, but got reply that its not applicable..

VIDEO

forum post:
https://forum.unity.com/threads/workaround-custom-icon-and-preview-image-for-your-new-project-templates.1554800/