> IRC has, for all intents and purposes, been replaced by Discord.
Yeah you can keep saying that but it doesn't make it true.
IRC has what most people need a text chat. A lot of the new features that these new programs have are unnecessary. End to End encryption being the most useful one, fortunately there's things like Matrix.
> In other words, a large number of communities I frequented have re-formed in Discord, and are much more active.
A lot of communities don't have a Discord server/channel so how active are those ones?
I wouldn't correlate activity with quality either. Typically I have found I get better/more knowledgeable responses from mailing lists, those are as old as email itself.
> There's still a few holdouts, but it's usually just 3 or 4 good-ol-boys who haven't left the server for 12 years.
If anything the introduction of Matrix has meant those channels are even more active with bridges especially on Freenode and OFTC where such bridges are officially supported.
> It's interesting to watch contenders like gitter, slack, mattermost, riot/matrix, etc,
Gitter is accessible by Matrix, Slack I've never needed to use as with mattermost. There's just so many 'options' out there that.
For private business stuff I'd probably use Rocketchat because I can self host it and not depend on some other company. It's good for sharing code snippets.
Matrix, particularly Riot still needs to become more mature. It is not as mature and dependable as IRC yet for general chat yet.
The Matrix spec isn't even finalized and is subject to change. That said it is making good progress. Their effort in regard to bridges makes it far more appealing than any of the other dozen proprietary options. If anything has the possibility of displacing IRC it will be Matrix.
I have seen that already particularly for developer communities.
> falling to the rise of Discord, which was for gaming communities but now it's like the reddit of chat servers.
Yeah but that's not developers, and yet despite these subsections using it I've never had the need. Next year it will be something else. The only reason Discord is as popular as it is is because Twitch ran a very aggressive advertising campaign.
For gaming you still can't beat a private mumble server.