As part of my News Archive project, I am trying to add feeds from one major US newspaper per day. As a start, I used this Wikipedia page (which has a list of the top 10 US papers by circulation). Only 7 of 10 papers had feeds (Chicago Tribune, USA Today, and Newsday did not have feeds). Some of them have feeds by default because their sites are built using WordPress (there were no links to those feeds, but by going to sections and adding “/feed/” to the end of the URLs – voila! Feeds!
Another interesting possibility is the existence of sitemaps in XML format. It appears this is being done so that Google can index content. I used Claude to create a script for creating a RSS feed from a sitemap file (see Github gist here). I am going to start using this for sites that do not provide feeds.