Looks like you can already play with it (though it's still "very incomplete") https://typst.app/docs/reference/html/
"Despite its name, TeXmacs is not a front-end to TeX or LaTeX.[mHowever, TeXmacs documents can be converted to either TeX or LaTeX. LaTeX also can be imported (to some extent), and both import from and export to HTML, Scheme, Verbatim, and XML is provided; the HTML export is stylable with CSS (since version 1.99.14). There is a converter for MathML as well, and TeXmacs can output PDF and PostScript for printing."
[2] GNU TeXmacs:
[0]: https://github.com/wcshds/typst-math-to-mathml-converter
Surely both of these characterizations depend on the person? I can believe that integral_t^oo is idiomatic if that's what you're used to, and maybe it's easier to pick up from scratch, but, for someone long used to TeX, it just makes me wonder what other unpleasant surprises someone else will have decided are actually pleasant.