Discord has both private and public channels. I won't bother considering their threaded discussion offerings, because they're absolutely horrendous.

ActivityPub is primarily public. You have scoped visibility that enables things like private messaging, but there is no implementation that allows for federated private group discussions.

There are proposals and a few implementations, but they all rely on everybody else to implement the same proposal, otherwise messages leak out, and that defeats the entire assumption of the private group.

It's not an unsolvable problem, merely one that hasn't been successfully solved yet.

As for whether AP is a good fit... It'll work. At the end of the day you're exchanging messages. Whether they're long form or chat messages makes little difference.

Matrix just isn't up to it. It doesn't function the same really. It doesn't feel the same.

although XMPP doesn’t necessarily natively have video call, usually you’ll have an accompanying TURN server

The same is true for Matrix and the popular Ejabberd xmpp server has a Stun/Turn server built in, which makes it even easier to setup than what you have on Matrix.

P.S.: Matrix also isn't a messaging protocol. It is a distributed database protocol that has been abused for making a messenger with it.

You can't choose what order channels are in, for one thing

That might not be a bad thing. I hate Discord. That might come due to its usage though. It's just not made to organize technical support.

Well yes, that's the problem. Matrix is just used for tech/troubleshoot issues and it's buggy as hell.

It isn't a social experience like discord. It is a gap in the fediverse

It's totally possible to make a true 1-1 competitor to Discord but no one has done it yet.

Nextcloud Talk is probably the closest thing with federation. But Nextcloud is notoriously complicated to host. And for some reason super unpopular outside of Europe.

Stoat (formerly Revolt) is very close, both in functionality and UI. But is not federated (and has no plans to) and for some reason not very popular. Also doesn't come with the wealth of configuration and moderation tools that Discord does.

Matrix works but it's super slow, bug-ridden, and complicated to use.

Zulip is similar but I've used it fairly extensively and still have no idea WTF is happening. Also not federated.

Of course there's always IRC and whatever other ancient comms tools that still work fine but are very dated and lack functionality.

In what ways?

The Stoat development cycle is really, really slow. This is why it's just fallen away.

Its buggy, it just doesn't really look like Discord. It is a chore for new users to use. There's no useful community discovery.

Don’t go looking for a 1 to 1 drop in. That mindset won’t work much. Same case wit expecting windows to work the same as windows: they’re just different and have to be learned in their own ways.

Many people use it as forums.

Right, but it almost doesn't matter because no-one is actually using matrix in the same way they might use Discord. It just isn't being used socially for hobbies and interests and a part of that is it's design and bugs and tedium getting set up.

Nextcloud talk has federation?

Except it's completely gated behind Discord corporate servers, unsearchable outside of Discord, and all ownership lies with... you guessed it, Discord.

But oooh aah Nitro....