I would recommend Signal and maybe Tox (protocol, has several clients).
Signal is a nonprofit. They make it a point not to collect your data. Just the phone number. Military folks seem to like them.
Tox is not a centralized entity at all, anarchists seem to like it. Multiple Tox clients exist and use a common protocol and network. Messaging happens via peer-to-peer, lookups make use of servers. For messaging to occur, both communicating parties have to be online, so don't expect much convenience.