RSS Feed on a Marketo Landing Page

A Marketo LP can bring in any external data you want (just like any web page!).

No, it can't bring in external data via the Marketo server (server-to-server communication). But it can certainly bring in data from the browser side, by fetching it from an external service.

But that external service needs to accept cross-origin requests (CORS). An RSS feed, like most services designed for non-browser contexts, typically doesn't by default. But it could easily be added, your web team just needs to add the HTTP header

Access-Control-Allow-Origin: pages.example.com

to the feed response. (Where pages.example.com is your LP domain.) 

Then you can pull the data in and format it any which way you want.