These often contain malware or are fake files renamed to .iso that will brick your device.
The search for an is primarily driven by owners of aging Android TV boxes (e.g., Xiaomi Mi Box S, Nvidia Shield) who want newer features. Unfortunately, there is no plug-and-play ISO.
The process typically involves creating a bootable partition on your hard drive or a USB stick to run the system.
For stable Android TV, stick to official hardware (NVIDIA Shield, Chromecast with Google TV) or use the Android Studio Emulator.