Fire OS blocks installs from outside the Amazon Appstore by default. Here's exactly how to get around that safely and put Aptoide TV on your Stick or Cube.
This works the same on every current Fire TV model — Stick, Stick 4K, Stick 4K Max, and Fire TV Cube.
Scroll all the way right on the top menu.
Then select Developer Options. If you don't see it, you may need to enable Developer Options first from About → click your Fire TV name seven times.
You'll see a list of installed apps that can be granted install permission.
If Downloader isn't listed yet, install it first, then come back and toggle it on.
From the Fire TV home screen, search for "Downloader" and install the app published by AFTVnews. It's free.
You'll land on a screen with a single address bar.
Enter 4277094 and select Go. You can also type aftv.news/4277094 if you'd rather use the full shortcut.
Downloader fetches the Aptoide TV APK automatically — this usually takes under a minute.
Confirm the install prompt when it appears.
Select Open on the confirmation screen, or find it later under your apps row.
Downloader will ask if you want to delete the APK file after installing — deleting it is fine and saves storage. It doesn't affect the app once it's installed.
Most Fire TV install issues come down to one of two things: the unknown-sources toggle reverting after a software update, or a spotty connection cutting off the download partway through. Our troubleshooting guide walks through both, along with fixes for the classic "app not installed" error.
Aptoide