Apple is doing insane stuff with iMessage making SMS useless with Android. It is intentional manipulation. I’ve only seen it on some Apple kernels with the latest iPhone. My old man’s phone absolutely will not send or receive an SMS unless I message is manually turned off and then it won’t get iMessages. Apple has always been a shitty company, but this is next level insane. Just get and use the Signal app and ditch all the proprietary garbage and manipulative bs IMO.
Not sure of the exact issue but the best answer from Apple so far is that the issue is kernel related. I’ve tried every setting I can find and no luck. It could also be related to actual dual sim use. It could be carrier related, but it is less likely Android as I use Graphene OS.