New on the repo today, for everyone here building outside rss.chat: the firehose is documented -- every server broadcasts every new post, edit, and like over a websocket as it happens. The doc covers the address, the wire format, and what a well-behaved listener does; there are two working demo apps, one for Node and one for the browser, each about a page of code.
Docs: https://github.com/scripting/rss.chat/blob/main/server/docs/firehose.md
Demos: https://github.com/scripting/rss.chat/tree/main/examples/firehose
It's the same protocol FeedLand uses for its firehose, so a listener written for one can listen to the other.