Libre opensource version of Slack?
@eilis I like Riot¹ which is a front-end for Matrix². I use it with students and it works great for our needs.
1. https://riot.im/2. https://matrix.org
@KnowPresent @eilis it's up in the air still. We've been trying RocketChat over at talk.lurk.org. Personally I am more in favor of federated alternatives based on xmpp (conversejs.org or movim.eu are good webclients).
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!