MathML seems to be the technology how to embed formulas in web pages.

Consider adding support in openhtmltopdf.

There is a project based on flyingsaucer which adds this support: https://mvnrepository.com/artifact/com.github.rjolly/flying-saucer/9.1.1
(However, GPL licensed) Maybe this rjolly can contribute it to openhtmltopdf