Firesticks run a special
Amazon version of Android called FireOS:
It is simply a basic version of android and is usually based on an older version of android (ie. the latest FireOS 8 is based on Android 11)
The main thing to understand is that FireOS has NO google in it at all - no google maps, gmail, play store, .ect and especially
no google play services. So if your app depends on some functionality that requires any google-centric API, it will not run on a FireStick.
So, if your app doesn't require any google services, it should run just fine on firesticks.
Also, you need to design the UI of your app so that the user can FULLY navigate your app using just the firestick remote because the user can not "touch" the tv screen to click on any views - so this might limit which views you can include in your app.