Typst( https://typst.app/)
Is good Latex alternative which should be mentioned here. Their roadmap also features html as a target.
replies(5):
"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: