I can agree any Apple-specific lock-in is not good, however you're talking about the ability to chat on the platform and not going beyond just access to include whether we should be trusting our data to that platform—different questions. Both XMPP or Matrix have clients on all OSs, lack a phone number requirement, but can also both be self-hosted + decentralized, and with open specs and you can read the source on the encryption to validate the trustworthiness. These are the routes we should head and there's nothing stopping folks from using them today other than they don't have a for-profit entity to market them.
Obviously, this goes back to the root issue as there are philosophical reasons to straight prefer certain technologies—like the ability to side-load apps on your pocket computer—that you should try not to compromise on just because of peer pressure.
Obviously, this goes back to the root issue as there are philosophical reasons to straight prefer certain technologies—like the ability to side-load apps on your pocket computer—that you should try not to compromise on just because of peer pressure.