Hey, very interested in this as well. I have tried all the standard troubleshooting regarding MMS messaging but I am experiencing a similar issue with my brand new OnePlus12R running Google Messages.
Very specifically, I have full MMS/RCS functionality with other Android phones but I can neither send/receive, nor view/create a group chat containing iPhone users. This issue extends to MMS messaging (pictures, gifs, etc.) as I cannot use MMS with iPhone users (groups nor individuals) but it is functioning perfectly with Android groups and individuals.
In my family group chat I have 3 androids and 2 iPhones - this means I currently cannot view or receive messages from this chat (even from the android users). Attempting to recreate a group containing the two iPhones will cause all of my messages to fail to send. I can create a group chat with only Android users and I have full functionality.
MMS functions, SMS and Mobile Data are fully functional but all MMS with iPhones are non-functional.
I have reset the phone, cleared cache, reset/edited/added new APN, reset mobile network settings, toggled RCS on/off, toggled MMS/SMS group settings, uninstalled/reinstalled Google Messages app, recreated groups, tried APN edits including capitalizing, etc.
Any idea what may be causing this hiccup with iPhones?
