Hummm, that's why I searched on all options with no success 😉
glad to know I'm not crazy,
voip over nodebb
an ability that some users can have voice chat(VOIP) to a group members!
Real time Chat and offline!
The chat functionality actually works either if an user is offline and online, so that functionality already exists.
For VoIp, existed some plugins, that you can try (don't know if them still working):
Cool stuff, I don't need this now but maybe in the future !