W3IM (A great alternative for Slack for free)

To deploy server, Clone this repo and follow instruction from README.md.

W3IM is secure workplace messaging from behind your firewall.

- Discuss topics in private groups, one-to-one or team-wide

- Easily share and view image files

- Connect in-house systems with WebHooks and Slack-compatible integrations

- Video call with screen share (one to one or, group)