Use this if automatic update fails, the TV won't boot, or TCL Support specifically provides you a file.
If your TV isn't finding an update over the air, you can use a USB drive. Format a USB flash drive (at least 4GB) to . Firmware TCL 50EP660
: Firmware updates often include better calibration for HDR and local dimming, significantly improving picture quality for movies and games. Use this if automatic update fails, the TV
Most EP660 models use the RT51 (RT2851) chassis. Use this if automatic update fails
There are active communities (like @tclupdates) that track the latest Android 9 and Android 11 releases for the RT51 platform.