If you’re looking for a way to cast from your phone or PC to the Amazon Fire TV or Fire TV Stick, now that Amazon seems to have abandoned Miracast support, try sideloading the CastReceiver app. XDA forum user josuelopezv has discovered that it works well to add limited Chromecast capabilities to Fire TV devices.
Google is notorious for keeping their Google Cast protocol locked down to their own devices. That’s why you don’t find any Google cast apps available in the Fire TV appstore, while there are numerous Apple Airplay apps. There have been Chromecast apps released for the Fire TV in the past, but they didn’t last long before Google took them down.
CastReceiver works by implementing a local version of the Google Cast protocol. That allows it to work even though it is not sanctioned by Google. Unfortunately, that means it cannot be used to receive streaming media from most Chromecast enabled apps. What it’s best used for is casting screens from Android devices using the Google Home app and for casting tabs from the Chrome Browser on a computer.