Telegram channels are sort of unique in that they combine broadcasting read-only messages and having a full-blown chat, like any other group chat. Is there anything similar in federated messengers?
For now I have to split up my single community into a microblog on Mastodon and a group chat in Matrix and this is super inconvenient.

I know you can create read-only rooms in Matrix, but there's no way for people to comment under posts. There's also a beta support for channels in Delta Chat, but there's comment section either.

Delta Chat is working on exactly that. The problem is that it isn't really good for moderation in group chats! XMPP is fine for broadcasting too, but it doesn't have the same official channel feature.

Delta Chat is working on exactly that

That's so cool! If they manage to somehow provide support for reading older posts, it would be a straight up alternative to telegram.

XMPP is fine for broadcasting too

I think I tried XMPP before and there was no way to comment on those broadcasted messages. Is that still the case?

My solution has been using bots that bridge multiple apps and also do RSS and Telegram

I think that's the only way to go right now. I thought of making a bot that just reposts toots from Mastodon to mimick Telegram channel chats

The Movim XMPP client has an integrated blog feature that groups can use to write articles or make announcements, which can be commented on or subscribed to as well.

Cool, thanks! Will give it a try

Delta Chat is working on exactly that

Where can I look for updates on this? I found nothing about this on their forum and Mastodon profile