Since I downloaded iOS 14 way back when, I've been unable to send/receive photos or join group chats with non-iPhone users. This has been the case with 2 phones - an 8 and my current SE running 15.2.1 - and also my husband's older phone. We are both on Verizon. My brother is also an iPhone user but doesn't have the same issue, and he has a different carrier and I believe his newer phone is 5G. I have SMS, MMS, Group Messaging, and iMessage on. Apple suggests updating carrier settings, but there's no obvious way to do that in my phone.