Now there is another open source alternative: Matterbridge (https://github.com/42wim/matterbridge https://github.com/42wim/matterbridge) connecting: Mattermost,

Now there is another open source alternative: Matterbridge (https://github.com/42wim/matterbridge https://github.com/42wim/matterbridge) connecting: Mattermost, IRC, Gitter, XMPP, Slack, Discord, Telegram, Rocketchat, Twitch, SSH-chat, Zulip, WhatsApp, Keybase, Matrix, Microsoft Teams, NextCloud, Mumble, VK and more. The use case is simple: instead of using plethora of IM apps, have all your conversations in one place.