Along with Atom, RSS is simple enough (it's in the name) that you can add RSS support even for static sites. ActivityPub, the most popular carrier for ActivityStreams, is "designed around the concept of an inbox and outbox" <https://lwn.net/Articles/741218/>, requiring that the server itself provide support. If you know of a realistic demonstration of ActivityStreams-without-ActivityPub that establishes a pattern that can be appropriated for re-use elsewhere (e.g. on static sites), then ActivityStreams is worth discussing, but otherwise probably not.
It's my claim that for all the work that goes into Mastodon, Solid, etc, none of them will truly succeed without the ability for programmers themselves to effectively put them into practice on static sites, especially those associated with their GitHub profile using GitHub Pages. (I despise GitHub, FWIW, and really hate that so much of the world of development has settled there, but I can know what I know from seeing what I see.) When it's simple enough to do that, that's the point where non-niche productized services for non-programmers to do the same will start popping up and off-Twitter chatter will take off. Despite the inroads that Mastodon has made, I don't consider in non-niche; it's being held back by the same factors described here.
https://www.w3.org/TR/websub/ formerly PubSubHubbub was used to notify subscribers, but it was optional and subscribers would fall back to polling. WebSub could be a separate service.
The trickiest part is handling replies, which involves some cryptography to prevent spoofing. But this too could be done by polling, only then you only get replies from those you subscribe to. ActivityPub does this with crypto too IIRC.
It's my claim that for all the work that goes into Mastodon, Solid, etc, none of them will truly succeed without the ability for programmers themselves to effectively put them into practice on static sites, especially those associated with their GitHub profile using GitHub Pages. (I despise GitHub, FWIW, and really hate that so much of the world of development has settled there, but I can know what I know from seeing what I see.) When it's simple enough to do that, that's the point where non-niche productized services for non-programmers to do the same will start popping up and off-Twitter chatter will take off. Despite the inroads that Mastodon has made, I don't consider in non-niche; it's being held back by the same factors described here.