Does tex4ht ever produce acceptible output? Certainly. Many people use it for complex math-heavy documents. But, as far as I know, they are all in LaTeX, which is where essentially all the work has gone for years now, since that's where the users are.
I don't believe anyone has tried the Texinfo mode since Eitan died, and virtually no one uses the plain TeX mode. I don't know what bits might have rotted, etc. and it gives me the output It does not look that bad to me, given that the (unexpected I guess) goal is a minimalist "text where possible" math mode -- tex4ht was developed long before mathml or math existed in Unicode, so had to make do with what it could (rather like Info, for the same reason). To get mathml, you can get that too (for latex anyway; not sure what will happen in plain tex), with the mathml option. It can also output to mathjax and other things, but I admit the invocations escape my mind. A basic invocation for LaTeX to get HTML5 and UTF-8 output is: htlatex file.tex "xhtml,html5,charset=utf-8" " -cunihtf -utf8" And httex instead of htlatex for plain TeX, or httexi for Texinfo. Michal (Hoftich, the main maintainer these days) and I have tried to put some info on https://tug.org/tex4ht, but plenty is lacking. I'm sorry the documentation is not better. Life is short. tex4ht appears to run TeX itself to get information from the produced dvi, instead of (or as well as?) attempting to parse the TeX code. It's "instead of". Which is what makes tex4ht a far more adaptable system than latex2html, which does try to parse the LaTeX input on its own, which means it fails once documents get weird enough. But just for parsing math equations it should work well enough, I suppose. -k