I doubt that agents can make a product as polished as Slack. The status quo would indicate that's not the case as the prediction that SaaS would die has not panned out at all.

> The quality of Mattermost and Zulip was NOT exactly as polished as Slack.

Mattermost isn't actually all that bad and its mental model is pretty close to Slack, at least compared to Zulip. I actually prefer Mattermost to Teams, and would view it in the same ballpark as Slack.

> Deployment of such stacks was a problem. A complicate operational overhead.

Not at all! Their stack is actually very reasonable and quite easy to setup: https://github.com/mattermost/docker/blob/main/docker-compos...

Nowhere near the nightmare that self-hosting Sentry is like: https://github.com/getsentry/self-hosted/blob/master/docker-...

I'd say that in Mattermost's case the group calling functionality was locked behind a subscription as well as some other stuff last I checked, which makes it dead on arrival for many. It was quite nice software though, even before being able to vibe code your own (though tackling videos sharing and RTMP will be anything but trivial).

> Make pixel perfect clone of Slack or Jira with SQLite or ejabberd behind.

There's A LOT of functionality and features in Jira, the only thing that saves claims like that is that you probably don't use 80% and can just build what your company needs. I more or less did that for the hell of it (MariaDB + Garage + Dropwizard/Java + Angular/Spartan) and there was still so much supervision an changes that were needed - after pulling the Jira DB scheme and throwing about 60% of it in the trash (didn't need the automation), there was still A LOT of stuff to do and even the plans eat up a whole bunch of the context of the coding tools you intend to use, no matter how many checks and scripts you write to automate guardrails for when the models simply don't recall everything that is relevant.

For people who want to self-host something basic, there's already the excellent https://kanboard.org/ (very very fast)

For those that want something similarly depressingly slow to Jira while still locking some stuff behind a subscription (at least in the versions I tried) there's the passable https://www.openproject.org/

If those don't fit and you don't see anything exactly like what you need, you might try to build your own. But yeah, not a weekend project.