Empathy - Apps/Empathy - GNOME Wiki!
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.
Gajim - Full featured and easy to use Jabber client
Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.
IM+ - Chat everywhere! IM+ is the most widely used mobile IM app! Connect all-in-one to MSN, Yahoo!, Goo...
Creativity 365 - Cross-device content creation suite