Lemmy generates RSS for every community. Look for the little wifi-like icon next to the sort-by selection box on the community’s main page.

Example: https://programming.dev/feeds/c/programming.xml?sort=New

You can append .atom to various GitHub URLs and get a link that will work in many RSS readers.

Example: https://github.com/LemmyNet/lemmy/releases.atom

Lots of blogs have RSS feeds, even if the links aren’t displayed. To check, view the page source in your browser, and look for the href URL in <link rel="alternate" type="application/rss+xml" href="https://example.com/feed/" />