I got the 15 Pro two weeks ago and I cannot text non iPhones. Sometimes, they go through individually, sometimes not and never if within a group. The same as the person above! My settings have not changed. I have checked the usual issues SMS and MMS messaging... It is the group text situation that is a HUGE problem.
I have contacted my carrier T-Mobile and they said it is an issue with Apple. I contacted Apple and after talking with several people I finally got a higher up guy who said he has seen this before and everyone in the group text thread (the text threads with both apple and android) has to delete and empty the trash on that text thread and then it can be rebuilt but only if everyone DELETES the text thread. It seems that after paying this much money the iphone 15 should be able to talk to all android users!