I found a workable method. Teams can add a tab for websites so long as they are iframed. That is simple. Just create a html page with this code:
<body>
<iframe src='http://localhost:8888/?token=yourtokenhere' />
</body>
Thanks to Saurs Saurav for the instructions.
(source: https://medium.com/@saurssaurav33/embed-jupyterhub-into-a-website-via-iframe-467db865f269 )
The trick is that Teams will only import HTTPS not a local file. Then you need a local development server to run OpenSSL. I had an IT buddy set that up for me. For the amount of effort needed, we abandoned this approach and host the notebooks on the Teams OneDrive. They open in a local browser window, so outside of Teams, but when the files are updated it can trigger the Flows.