They refuse to make the Prime Video app available on the Play Store, they refuse to add Chromecast support, and now they refuse to even sell Chromecast because of their own decision to not support it? I've just canceled my Prime subscription and I hope a few others do as well.
You need the amazon appstore app, to install it, and you need amazon shopping app installed to run it (have no idea why). It works fine on android once you have installed all the amazon bs, but last time i checked the app wasn't very good on iOS.