Mercury certainly seems worthy of keeping an eye out.

Voila is the obvious competitor to this. There are also different oranges and apples such as Dash, Streamlit, Panel: https://anaconda.cloud/dashboardlandscape - obviously Anaconda is a bit biased here.

I suppose the biggest limitation to Mercury is the limited number of widgets. Good for quick demos.

Also deployment is a bit unclear at the moment - I wonder how easy it is to keep Mercury deployed in a separate Docker container - that is I do not want to keep random ports open on my notebook server.

Then again probably deployment/hosting is how Mercury expects to make some money.