Shtuff Chat - Free Group / Team chat with persistent history.
Microsoft Teams - Microsoft Teams provides the enterprise-level security, compliance and management features you expect from Office 365, including broad support for compliance standards, and eDiscovery and legal hold for channels, chats, and files.
Meet in Chat - Meet new people. Have fun sharing photos.
Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.
Kandan - Open Source private chat server. Your own private Chat server in minutes, plus additional features.
Creativity 365 - Cross-device content creation suite