For my the best choose is XMPP… More choices, federated, simple and very secure with Omemo. You don’t have the security issues like you do in WhatsApp, Telegram or Matrix (who’s principal server is in economic problems matrix.org). And Signal… Well it’s a long journey and can take very bad turns cause is private and has big ties with the US and big corp, still is and option and you can use the fork Molly.