Matrix has "rooms".

Do rooms work like a blog/feeds/readers? I thought they were more like Signal's groups.

I think threaded discussions are planned, but so far it is only for linear discussions.

That's very different from the relevant Telegram groups. Those function more like a blog on the web — non-subscribers can search for them, only the group's owner(s) can post, and everyone else can just read. And they work for very large audiences, 100k readers is no problem.

I see. With matrix rooms it is possible to set permissions in a way that only the owner can send messages in that room. There are also large(-ish) rooms, such as #/room/#matrix:matrix.org with > 30k users, but I think threaded discussions would allow for a functionality that resembles a blog where subscribers can comment on articles. And there is a preview functionality that technically allows users to read public rooms without being subscribed.

Of course Telegram is quite a bit more polished and fun to use than element or other matrix clients so far.