Bluetooth controller input is not working correctly in Build 510649 from Amazon Appstore. Left stick works for movement, but no other buttons are recognized for actions nor key binding assignment. Verified across three generic BT controllers and three devices (Moto Z Droid, Nexus 7 (2013), Kindle Fire 7 (2015)). Replacing app with Build 510646 from Google Play Store on the Moto Z and Nexus 7 resolves the issue, but this isn't a direct option for Kindle Fire. The same three controllers work correctly on Fire TV (2nd Gen).

Possibly related to:
https://bugs.mojang.com/browse/MCPE-24594
https://bugs.mojang.com/browse/MCPE-24928
https://bugs.mojang.com/browse/MCPE-27334