Regarding the IM/Slack alternatives you can maybe consider adding Movim ( https://movim.eu/ https://movim.eu/ ). Fully based on XMPP with plenty of features alr

Regarding the IM/Slack alternatives you can maybe consider adding Movim ( https://movim.eu/ https://movim.eu/ ). Fully based on XMPP with plenty of features already packed in. It can easily be deployed on a simple web-server. PS: I'm the author and maintainer