Apparently some people are still under the mistaken impression that #XMPP is too hard to join compared to #Signal ...
(Snikket is great, but not everyone is willing to self-host.)
They usually aren't aware of Quicksy. It's a libre XMPP client (available for free from the Play Store and the App Store) and service. Quicksy uses your phone number to register - you don't need to spend time selecting a server, nor remember usernames and passwords. And it discovers contacts using phone numbers too.