@antichrist_hater @tost @amd64sucks that's what ActivityPub is, actually
you're probably looking for the `toot` context (defined by Mastodon)

https://rhiaro.co.uk is a completely valid and probably the most standard ActivityPub service (much more standard than most fedi software, in fact) and i don't believe Mastodon, Pleroma, Misskey, Honk or whatever I can currently think of federates with it or can communicate with it