There was Bibliogram but it closed as it was impossible to keep up with Meta’s barriers, sadly

OP says the kid has been “all over scratch” so we can assume they need something more

It’s another Chromium/Electron based app, so it may not be suitable for low end systems, but still, it’s weird that it doesn’t load at all. I don’t know how to help, sorry.

I find it pretty inefficient to start up a Python environment, a web server and a web browser to do something that you could do with Notepad or even in a terminal. I would use Notepad++, gedit, Kate, vim, vscodium… There are plugins for vscodium (and vscode obviously) to preview Markdown if that’s what you need