We tried Mattermost a while back. Slack is just way more polished, especially the mobile apps. We use the API to interact with Slack a lot. Mattermost was fine, just not nearly as nice as Slack.

I've never used Slack in a business context which leads to: what polish is missing that actually affects your use case? You mentioned mobile for instance but how are people using the mobile app while also being in an actionable position?

Not everyone is a programmer! I've had plenty of times when I was getting messages on my phone that mostly required informing/connecting the right people/departments. If I hadn't done it stuff would have eventually gotten done, but a lot later & with more misunderstandings and miscommunications.

You could probably roll your own with Riot & Matrix, but it's probably not as feature-rich as Slack or Mattermost.

Past HN discussion: https://news.ycombinator.com/item?id=17031306

We use Zulip which is an unfortunate mix of awesome and mediocre.

Like Mattermost Zulip can be self-hosted, although we use the online paid for version.

Zulip's USP is the 'topic' system which group messages in each thread into a coherent conversation. It makes it much easier to look back over a set of conversations and see what happened. It works really well. It's let down by the mobile apps though, which are clunky and don't behave reliably.

The web-app is excellent though and the topic system does (just) win out over the crap apps. I do wish they'd sort them out though, both for me and so I could make an unqualified recommendation.

Same here. I like it but it does lack some of the features and polishing you get with Slack. I find that the Windows client leaves a lot to be desired. I have to restart it constantly because it becomes painfully slow. Channel "unread visualization" is unreliable. The search is pretty bad. Things like that.

You might also checkout zulipchat. I've been advocating for us to use it internally (over M$ Teams) for a while now.

Discord is way more polished than both

Discord is not more polished for decent sized companies who need to worry about regulatory compliance and things.

Was in the same boat at my previous company, we used Mattermost because of privacy concerns with Slack. Eventually moved to Slack because the mobile options were not great on MMost and Slack was more polished.

Boy, I mentioned Slack a lot.

RocketChat too

Used it. I don't think anyone liked it too much. Switched to Zulip, which seems a little less objectionable. Still I'd prefer good old IRC.

Bitrix24 is much better in that respect IMHO. Both cloud and on-premise editions, and you get not only chat, but tasks and projects as well.

we use it. we're a pretty big company too. like it.