When developing KeenWrite[1], I opted to support only plain TeX. This is because I wanted math typesetting to work for either LaTeX or ConTeXt[2]. To render TeX in the preview panel, I forked NTS[3] into a highly optimized Java version. The lack of cross-platform event-based UI system is what kept me from writing the entire application in Rust (some ten years ago). Has the Rust ecosystem improved with respect to Markdown processing, event-based UIs, and now TeX support?

[1]: https://keenwrite.com/screenshots.html

[2]: https://wiki.contextgarden.net

[3]: https://ctan.org/tex-archive/systems/nts