Here in Paraguay internet services can be "spotty" and lately (intercontinental) Skype communications are suffering because of that. Slack was presented as possible alternative. Although it looked kinda powerful, the need to "sell" the others on this one wasn't something I was looking forward to. Mainly because it looks like you need to communicate through their servers.
Anyway, I started to look at alternatives for slack, and found Mattermost. This one is powerful, allows for fine grained authorization schemes and supports even Markdown. Best of all, I can host it myself, there are Android/iOS clients and there are projects that say they can integrate email and the Jira issue tracker into it too. After setting up a test server and local test session (because Skype was failing once again), the general consensus was that we liked it. But the lack of VOIP/Video calls would still make it a hard sell.
But now I see that there is Riot
, which appears to do everything that MatterMost does on web, desktop, Android and iOS, but also includes (conferencing) VOIP/Video calls.
How Slack compares with Mattermost
according to the Slant website. Unfortunately there is no indication when which versions of Slack an MatterMost were compared with each other, so some of the listed Pros/Cons might not apply anymore.
Still, the 'vs.' feature on this website allows for a lot of alternatives to be pitted against each other. Unfortunately I didn't see Twist App in this 'vs.' list.