There should be some utility that can look through all your bookmarks to see if any of those sites have a RSS feed. Or at the very least there should be some site where you can submit like 100 different URLS and have it batch search to find a RSS feed.
batch search URLs for RSS feeds from your bookmarks
Happening right now on Spudart: Press a leaf in an envelope with the date and story written on it until 2026-10-31
http://search.msn.com has a rss feed search. You can submit multiple sites if you use the correct syntax. If you type in the search bar something like: (site:www.cnn.com OR site:www.spudart.org) (feed:) this will search spudart.org and cnn.com for rss feeds. You could build up the site string with as many sites as you want. Maybe it’s not exactly what you are looking for… you could create a program that extracts your favorites and formats them for search.msn.com. Or you could create a web page that lets you add a bunch of urls and then sends them to search.msn.com