Amazon's newer Fire TV Stick 4K Select (2025) and Fire TV Stick HD (2026) run Vega OS instead of Fire OS. They only install apps from the Amazon Appstore, so apps like TiviMate cannot be installed on them.
How to check your stick: open Settings, then My Fire TV, then About. If it does not say Fire OS, you probably have a Vega OS model.
If you already own one, tell us below which player apps you found in the Appstore and how they work with an Xtream Codes login. If you are buying a stick for IPTV, the Fire TV Stick 4K Plus and 4K Max still run Fire OS.
Full guide: https://iptvnord.ca/installation-guide/amazon-fire-tv-stick/