Finding Feeds
AutoFeeds supports RSS 2.0, Atom 1.0, and JSON Feed 1.0/1.1 feeds.
Bluesky
Bluesky provides RSS feeds for user posts. All you need to do is add /rss to the end of a user’s profile link. For example, the feed for the Bluesky account ‘@vale.rocks’ is https://bsky.app/profile/vale.rocks/rss.
Reddit has very robust RSS feed functionality which can best be referenced here: https://old.reddit.com/wiki/rss
YouTube
YouTube channels have RSS feeds. They’re a tad tricky to retrieve, so it can be convenient to use a tool to fetch them. As an example, the feed for the OuterVale YouTube channel is https://www.youtube.com/feeds/videos.xml?channel_id=UC8hQBcgwkZiG-cqhE1TDvzA.
Steam
Steam games have RSS feeds for updates and news. You must add /feeds after store.steampowered.com but before /news. For example, the feed for the news page for Terraria is https://store.steampowered.com/feeds/news/app/105600,
Steam groups also have RSS feeds. You must add /rss to the end of the URL.
Tumblr
Tumblr blogs have RSS feeds for all posts. They’re found by appending /rss.
GitHub
GitHub provides an Atom feed for releases. You must append .atom to a releases page. For example, the feed for releases of the Stoat backend is https://github.com/stoatchat/stoatchat/releases.atom
Tangled
Tangled provides an Atom feed for releases. Append /feed.atom to a user’s profile page. For example, https://tangled.org/vale.rocks/feed.atom.
An Atom feed is also provided on a per-repository basis. It can be accessed by appending /feed.atom to a repositories page. By default this feed will include issues, pull requests, commits, and tags, but you can filter this with the include query parameter. For example, to get just the commits and issues: https://tangled.org/vale.rocks/AutoMod/feed.atom?include=issues,commits. The possible includes are issues, pulls, commits, and tags.
Letterboxd
Letterboxd provides an Atom feed for user activities. For example, the feed for CharliXCX’s latest watches is https://letterboxd.com/itscharlibb/rss.
Behance
Behance has an RSS for users. You must add the user’s handle to the end of this URL: https://www.behance.net/feeds/user?username=.
DeviantArt
DeviantArt fully documents their RSS feeds: https://www.deviantart.com/developers/rss
Pinterest provides an RSS feed for user posts. You must add /feed.rss after their username in the URL. For example, the feed for the official Pinterest account is: https://www.pinterest.com/pinterest/feed.rss
AutoMod Blog
Like many blogs, the AutoMod blog provides feeds. The RSS feed is https://automod.vale.rocks/blog/feed.xml and the JSON Feed is https://automod.vale.rocks/blog/feed.json.
Hacker News
Hacker News has a solid variety of feeds availiable. Notable are: the front-page (https://news.ycombinator.com/rss), newest (https://news.ycombinator.com/newest.rss), Ask HN (https://news.ycombinator.com/ask.rss), and Show HN (https://news.ycombinator.com/show.rss).
You can also use external services, such as Hacker News RSS to create a wider, more tailored variety of feeds.
Lobsters
Lobsters has a feed of all stories (https://lobste.rs/rss) and all comments (https://lobste.rs/comments.rss). Specific tags also have their own feeds, for example: https://lobste.rs/t/retrocomputing.rss.
Other Sites
If you’ve gone looking and can’t find a feed for a site, look into Open RSS which goes looking for you and will generate a feed for sites that don’t have them.