Matrix
Matrix is an open-source, decentralised and secure communication standard.
Chat RegisterXMPP/Jabber
XMPP/Jabber is an open-source, decentralised and secure communication standard.
Chat RegisterGitea
Gitea is an open-source (source code) version control software.
CodeMumble
Mumble is an open-source, decentralised and secure voice chat.
Talk