Dialog Messenger - handy and feature-rich enterprise multi-device messenger available for server or cloud – Slack-like, but not Slack-limited
RemindUs - Advanced reminders for Slack teams
Ripcord - A desktop chat client for Discord and Slack
Slack - A messaging app for teams who see through the Earth!
Ziggs - Smoothly Share Content Between Devices!
Workplace by Facebook - Connect everyone in your company and turn ideas into action.