Upgrading an Android TV from version 4.4.4 (KitKat) to 5.0 (Lollipop) can be achieved through official over-the-air (OTA) updates or manual methods if an official update is no longer supported by the manufacturer. Note that many older TVs have hardware limitations that may prevent upgrading to newer versions.
A: You’re trying to install an unofficial ROM on a locked bootloader. You need to unlock the bootloader or use a custom recovery.