This site frequently hosts AKAI and LDD board firmware. Search their database for "AKTV5537S" or the board number "LDD.M538.B138". Firmware.VIP: A common repository for 4K Smart TV firmware.
The firmware files for the (mainboard LDD.M538.B138 ) with a 3840x2160 resolution are typically hosted on specialized electronics repair and firmware archives. This site frequently hosts AKAI and LDD board firmware
Use a high-quality USB 2.0 drive formatted to FAT32 . This site frequently hosts AKAI and LDD board firmware