This is great!

If it's useful, I work on a project where we maintain a repository of XPath selectors for extracting article content from many different sites: https://github.com/fivefilters/ftr-site-config - they're based on the original public Instapaper rules.

We also have PDF generation, but it's not really for crawling, and wasn't created for reading on a device like the Supernote, more for printing and reading: https://pdf.fivefilters.org/simple-print/