Search for "Smart TV Software" channels like hashmielecom which list factory codes and software files for various MS338 series boards. Installation Warning
To access the service menu, use the remote sequence Menu + 1147 . Download MS338 PB803 1366x768 Stream part08 rar
Firmware for these Chinese universal boards is usually hosted on specialized technician forums or shared via cloud storage links: Search for "Smart TV Software" channels like hashmielecom