Rendering to SVG, at least that's what I did on https://fschutt.github.io/printpdf/

I am currently writing a WASM-ready PDF toolkit that can handle both HTML to PDF and then rendering PDF pages to SVG. However, it's not yet production-ready.

The underlying HTML engine is currently a severe "work in progress", but it gives me the low-level access that I need: https://azul.rs/reftest