https://arstechnica.com/gadgets/2024/09/ios-18-brings-rcs-to-major-carrier-iphones-but-prepaid-plans-are-still-waiting/

The future of inter-OS mobile messaging is here, it's just unevenly distributed.

With iOS 18, Apple has made it possible for non-Apple phones to message with iPhones through Rich Communication Services (RCS). This grants upgrades from standard SMS text messages, like read receipts, easier and higher-quality media sending, typing indicators, and emoji/response compatibility. More than that, it allows for messaging while on Wi-Fi without cellular services and makes group messages far less painful to navigate and leave. Notably, RCS messages between iPhones and non-iPhones will not be encrypted, like Apple's private iMessage service available exclusively between Apple devices.