Here’s How to Send Texts on an iPhone Even if You Lose Cellular Service
New York Times
All iPhone 14 and later models can connect via satellite, but your phone must be updated to the latest software, iOS 18. Recipients of the messages must also have the latest iOS. Android users with Pixel 9 phones also have some options.
https://www.nytimes.com/2024/10/09/us/milton-iphone-texts-satellite-emergency.html