Fire OS 8 changed sideload flows, tightened per-app permissions, and broke half the old tutorials. These picks work on every current Fire TV SKU without tricks.
If you want 4K IPTV: the Fire TV Stick 4K Max is the minimum. The Lite and non-Max 4K struggle with some HEVC 10-bit streams. If you're in the Apple ecosystem and already own an Apple TV 4K, that's a better playback device — but Firestick remains cheaper per TV.