Microsoft Teams alternatives

Microsoft Teams
Microsoft Teams is the chat-based workspace in Office 365 that integrates all the people, content, and tools your team needs to be more engaged and effective. Microsoft Teams free open-source (self-hosted) alternatives are: Mattermost, Rocket.Chat, Zulip
Microsoft Teams alternatives are:
Slack, HipChat, Yammer, Skype for Business

Here are the latest news about Microsoft Teams:

20.10.17 Microsoft upgraded Teams for Enterprises

Microsoft announced a significant upgrade to its Teams collaboration app this week, bumping up the number of people allowed in a single Team from 999 to 2500. When Teams launched last November, people speculated the app was Microsoft's answer to Slack and Stride for Office 365. But with the original Team size limit of 999 people per team, Teams remained an attractive option for small-to-medium enterprises, but held limited appeal for larger organizations. Since its release, one of the most frequently requested improvements from users was an increase to that limit. For companies with over 15,000 employees — in other words, the companies Microsoft appears to be targeting — a 2500 limit is unlikely to be a big enough increase. The conclusion is that Microsoft Teams becomes more enterprise-ready in comparison to alternatives

2017 Microsoft Teams will replace Skype for Business

2017 Microsoft Teams adds guest access

2017 Microsoft opened Teams to all Office 365 users

2016 Microsoft introduced Teams - the main Slack competitor