Forum How do I...?

I don't even know what these are called. Underline cutouts for descenders?

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

John Haugeland is

This is text-decoration-skip-ink

The CSS Working Group has defined this

There's some browser support

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! :D