Let's chat, Zulip, Kaiwa, Mattermost there are probably a hundred more. Depending on the Scale, I'd personally go with an own Kaiwa Fork, backed by an Erlang M

Let's chat, Zulip, Kaiwa, Mattermost there are probably a hundred more. Depending on the Scale, I'd personally go with an own Kaiwa Fork, backed by an Erlang MongooseIM Backend and LDAP.