Does prince know how to cut the underline to accomodate descenders, ideally with a spacing?

John Haugeland is http://fullof.bs/

No.

This is text-decoration-skip-ink

The CSS Working Group has defined this https://drafts.csswg.org/css-text-decor-4/#text-decoration-skip-ink-property

There's some browser support https://caniuse.com/#search=text-decoration-skip-ink

It's not widely supported across browsers or for that matter supported by Prince, but the CSS property you're looking for appears to be text-decoration-skip-ink which makes the term, I suppose, "ink skipping" or "skip-ink underlines". Depending on how fixed the text is one thing you might try is rendering the text as an SVG and then importing that? Granted, it's not the most accessible or straightforward of methods.

You can allegedly do sneaky tricks with text-shadow to try and replicate this on the sly, although I would probably not recommend it!