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Or WhatsApp, if you want to message people who aren't on ios.

Or signal, which has similar functionality but is always end to end encrypted and open source.

...or Matrix, or XMPP, which are decentralized and where attaching your phone number to account is optional.

And don’t mind Facebook having your data.

Keybase is where it is at. Even my parents are on it. Group messages that work and some attempt at security and privacy - all for free-99.

Don't forget about Signal. It works great as an sms replacement