“Phone number registration is not working yet. All users must now sign in with an AppleID. Messages will be sent and received via your email address rather than phone number. We’re currently working on a fix for this.”

I guess if your iPhone friends have your email it will work. I’ve never used Ios so I can’t speak to how it looks on their end. Other solutions using email are out there as well though they require you to own a Mac to run a server.