Terminology nit: s/encrypted/secure/ - lots of systems that have encryption are pretty insecure.
As to the question, how about OTR+XMPP or Signal. Signal desktop is in beta. I don't think you need to worry about running the desktop Chrome extension on iOS since there's a native iOS app too?
As to the question, how about OTR+XMPP or Signal. Signal desktop is in beta. I don't think you need to worry about running the desktop Chrome extension on iOS since there's a native iOS app too?