Note that there's also streamlit [1]. It uses regular python files, rather than notebooks, so they can be easily version controlled. And it has more UI tools.
I can create a GUI for a tool that looks nice faster than I can make a CLI. I've built useful production systems (ok, sure, for internal use) in literally minutes.
You're a bit limited in what kinds of apps you can make but the tradeoffs it makes here means that it's astoundingly easy to make a wide range of very useful tools.
https://data-dive.com/multi-os-deployment-in-cloud-using-pyi...
It uses pyinstaller to build and even pushes the build as a zip into your release page on github and appears to be working quite well.
https://news.ycombinator.com/item?id=19859913
As a note to OP, messaging your solution as “turn your notebook into an app” may not be optimal — you will loose many who abhor working in notebooks.