As a python developer and user of websites, please no. The web is already a slow mess and my laptop is already spinning up fans on some websites that really shouldn’t do anything much more complicated than load text and images from a database and display them. CPython would make it exponentially worse. At least pick a sensible performance focused implementation.

Why though

It will be a cold day in hell when I consider using any software running on Someone Else’s Computers ™ for journalling or note taking. Even less so when there are a number of FOSS, self-hostable, highly configurable and feature-rich solutions out there (I personally am partial to Trilium).

How is it a “trap” to spend an hour or two configuring a tool to your exact needs, which you will then probably be using literally every day for years.

why linux will never be a viable solution on the desktop

Has been pretty viable for me for the last 7 years or so.

why self hosting will never take off

Literally who cares, the community stands to gain nothing from another few million novice users who don’t even know or care to learn how to formulate a question or usable bug report.