i'm going to make a radical claim:
the "phone" has basically ceased to exist.
these devices we call phones? they're pocket computers that just happen to have cellular connectivity. they should be treated as such - which means open specs, unlockable booting, replaceable operating systems.
if you need to blob the cellular bit for regulatory approval, fine, do that, but agree a standard interface to it (like AT commands for old modems, or the interface to the Pi's GPU capabilities) that all OSes can use on all cellular devices. but there's no excuse for locking down any of the rest of the device, is there?
@vxo @thamesynne I've issued AT commands to my phone's modem to correct the phone number stored in the sim card. it's quite simple on rooted android