Sphinx/reStructuredText supports math in LaTeX input format [1], so you can still go nuts with complex math expressions while still benefitting from the relative simplicity.
I have documented at least 10 x 10 matrices with rst math directives and found it to be pretty convenient. I don't understand what the benefit of pure latex is in this context.
MyST-Markdown supports MathJaX and Sphinx roles and directives. https://myst-parser.readthedocs.io/en/latest/
jupyter-book supports ReStructuredText, Jupyter Notebooks, and MyST-Markdown documents:
You can build Sphinx and Jupyter-Book projects with the ReadTheDocs container, which already has LaTeX installed: https://github.com/executablebooks/jupyter-book/issues/991
myst-templates/plain_latex_book: https://github.com/myst-templates/plain_latex_book/blob/main...
GitHub supports AsciiDoc in repos and maybe also wikis?
Is there a way to execute code in code blocks in AsciiDoc, and include the output?
latex2sympy requires ANTLR.