By ROM... I mean like a flavour/distro of Android OS.
There are devices that technically CAN do Miracast, but were never granted the ability from the OEM in the first place.

There's people who port custom ROMs from other Android devices to these Android devices. In all* cases, Miracast never works and the camera (until alot of development) and some other sensors and functions.

Its because Miracast has to run some sort of certification during the pairing and it has to remain active throughout the connection. Its there for good reason, but its still a wip. And its implementation is very "beta" on Android and basically non-existent on other devices.

Miracast is pretty much dead... unless some company (not Intel) can lift its mantel