Agreed. Having an open-source alternative to (the otherwise excellent) Typora would be fantastic; as far as I can tell the main feature Ferrite is currently lacking to be used for most (all?) applications where I use Typora is a way to easily write and render maths formula. (As far as I am concerned, support for TeX math would be ideal due to wide support from the existing ecosystem; but Typst would work too.)
Thanks! TeX math support ($...$ and $$...$$) is planned for v0.4.0. We're going pure Rust (no JS runtimes), targeting common LaTeX syntax. See the planning doc on github (docs folder) for details.