My experience is directly the opposite. Bought an iPhone 12 Mini after Pixel 3XL died. Granted, I was already using a Macbook for a long time. Lotta things I’d been trying to get working, using things like KDE Connect instantly became automatic.
I’ve seen people actually get job done on phones, but that’s never been the case to me. To me the phone should ideally be an extension of my desktop. I’d been doing that with Chrome+Pixel for a while. But iPhone unlocked much more of macOS for me
This seems to imply that you need a fork of Android, if you’re to build a messaging app that uses RCS.
But my understanding is what you really need is essentially an RCS server.