Thank you.
I have found that lib, flashrom + frser-duino. even flashrom + PICkit2. But all that I never tried. Thank you again for suggestion.
Hence, I have made years ago 3.3V power supply for arduino (328p) clone. It would be extremely slow through UART, however at least do not require special programmer.
I have already change all caps on power supply board with branded ultra low ESR, as well on MB and confirmed back light works correctly, however problem persisted. After calling official service, they recommend changing the memory chip with latest firmware.
I suppose TV use some specific blocks to save current configuration and various settings with probably including CRC and load/check during turning ON / Wake up. Datasheet for 25Q32 state 100 000 E/W cycles, which is about 55 E/W cycles per day and then seems quite possible to fail after 5 years, if save status periodically or on standby...
In any event, if changing the chip also fail, TV will probably finish in recycling center.