I’m in a group message thread with Android and iPhone users, but I can’t receive images from the Android users via SMS.
iOS 18.1 Beta 5 - Can’t receive images via SMS
You should probably raise this as a bug in the usual way. It won't really get progressed if it's only posted in these Developer Forums.
You need to raise each issue you find separately at https://feedbackassistant.apple.com/ You can post the FB numbers here if you want, so that others can link to them.