Mstar MSD6369IV (32-bit SoC with 1 ARM core and 1080p Full HD GPU).
Technical resources like KenotronTV outline a two-step recovery process if the TV is stuck in a boot loop ("SmartTV loading" screen): Download 35019017 1920x1080 DNS 42AK9000 part1 rar
KPS-L090C2 (utilizing TEA1733 and 4N60L chips). Flashing & Recovery Process Mstar MSD6369IV (32-bit SoC with 1 ARM core
If the USB method fails, the eMMC chip must be desoldered and flashed with the firmware image (User and ExtCSD partitions) using a programmer. Official Resources Download 35019017 1920x1080 DNS 42AK9000 part1 rar
For official drivers and documentation, you can visit the DNS Support Page for the 42AK9000 model.