The only app that works well for me is Conversations (XMPP client). It's also quite battery efficient. You have to convince people to use XMPP though, that's th

The only app that works well for me is Conversations (XMPP client). It's also quite battery efficient. You have to convince people to use XMPP though, that's the hard part. For all apps that requires Firebase/GCM, the only solution is MicroG, but then you have some data going to google. It doesn't require a google account and, depending on how the app is made, it shouldn't contain personal data, but it's still data going to google...