You can find the firmware files and parts at the following locations:

Offers the MS338 PB818 USB firmware for specific resolutions including 1366x768.

Provides access to the TP.MS338.PB818 EMMC rar file and other related parts in their archive.

Ensure you match the specific panel model and remote type before flashing to avoid "bricking" your television.

The MS338 PB818 1366x768 firmware is available for download across several specialized LED TV software repositories. These files are typically used for USB flashing or EMMC recovery for Android smart TVs using the mainboard. Download Sources

Varies by version (Global Logo, Noble Remote, or Samsung Remote).