[LinuxBender]

I would agree a voice call is useful for a warm hand-off and sometimes easier to convey a message without excess typing. That is where Mumble (murmur server, self hosted) makes sense to me. Clean quality voice plus text chat for links and what-not. [1] There are public servers if you want to try it out first before setting up your private servers.

[1] - https://wiki.mumble.info/wiki/Main_Page

Try their snapshot / rc versions. They are quite stable. Not as happy-clicky as Discord, but more more private and secure.