Ideally, SimpleX (https://simplex.chat/). Session is nice, but less secure (https://getsession.org/). Delta Chat (https://delta.chat/en/) will be secure enough, and the most familiar visually. Lastly, XMPP is a great solution as well.
Ideally, SimpleX (https://simplex.chat/). Session is nice, but less secure (https://getsession.org/). Delta Chat (https://delta.chat/en/) will be secure enough, and the most familiar visually. Lastly, XMPP is a great solution as well.