I was looking for the NYT RSS feeds. So I typed in “site:nytimes.com rss”. In Kagi it says no results, but on DuckDuckGo it does what is expected, it searches the New York Times website for the term “RSS” and found the result I was looking for. Perhaps there is a different way to trigger a site specific search, but the “site:example.com foo” method should work too.
Type site:example.com to restrict search to that site.