I'd like to update my response since discovering jitsi.
It's Jitsi.
Have used this recently for instant work convos. Down and dirt simple, easy on the eyes, low footprint, encrypted, intelligently thought out, no membership/signup and makes me want to cancel my zoom sub. It's far from a face-to-face app if you want it to be that way. Versatile.
Brucehankins --would you accept an app in the chat category that required a formal invite/accept model?