To embed a Dash app as an iframe, run the dash app in a separate python process and then use the iframe markup to embed it by URL:
<iframe src="the-url-of-your-dash-app" style="border: none;"/>
There are not any better solutions to this right now, however there will be in the future. If anyone reading this would like to sponsor the development of a better solution, please reach out: Consulting, Training & Open-Source Development