Also not free, has banking ramifications, etc.

TFA mentions that Mattermost's source is AGPL and the binaries are MIT. It's absolutely free software.

It's also $0 software, in that it being free software and open source, you can simply and legally patch out their license checks and recompile, if you so wish.

I was referring to the VPS hosting, not the software.

Ease of hosting is one of the very biggest advantages to something like Slack or Discord.

Or just Matrix.

Still harder than Slack, right?

How is slack any better than discord? Both roll out stupid (and forced) updates, and slack doesn't even let me browse kinda old history if the owner doesn't pay for it. [*4] Not to mention the search is relatively terrible anyway.

The main thing that worries me about is discord is their revenue model... I just don't see how they're making money, and they keep on raising money.

There are a few good alternatives like zulip [0], matrix [1], discourse [2], Rocket Chat [3], or just plain old irc.

Although discourse isn't really a chat application but more of a open source forum software.

[0]: https://github.com/zulip

[1]: https://www.matrix.org/

[2]: https://github.com/discourse/discourse

[3]: https://rocket.chat/

[4]: You can get around this by messaging relevant information to yourself. Or just saving things locally, like a weirdo.

If you check the parent I was replying to, it was about Mattermost being harder to set up than Slack.

I never said anything about Slack or Discord being better/worse than each other.

And RocketChat no?

Ah, right. I should amend the parent as there are a few other open source alternatives. That said, matrix (from what I can tell) is much more widely used.