XSLT

 XSLT  (eXtensible Stylesheet Language Transformations) is a styling and transformation language for XML. It can be used to style an XML feed file like RSS or Atom so that it can be opened in a browser with visual styling.

Anthony Ciccarello
publishes an Atom feed with XSL styles so that the user experience will be less jarring if someone clicks on a link to the feed file from his website since 2021-04-17. The approach is described in a blog post.

Peter Molnar
has a links OPML, along with an XSL stylesheet to make it human readable in the browser.

Hsiaoming Yang
Hsiaoming Yang has used XSL to format a human-readable RSS feed on his website
 * Details: How to style RSS feed