While messaging Android to Android or iPhone to iPhone is secure, messaging from one to the other is not.
Now even the FBI and CISA, the US cyber defense agency, are warning Americans to use responsibly encrypted messaging and phone calls where they can. The backdrop is the Chinese hacking of US networks that is reportedly “ongoing and likely larger in scale than previously understood.”
Fully encrypted comms is the best defense against this compromise, and Americans are being urged to use that wherever possible.