To do a firmware update, you have to have a functioning television.
If it's actually showing a screen that's in bootloop, the 30800-000499 mainboard will require removal and flashed with special tooling. These boards are only $25 USD / $40 CAD, making it easier and cheaper just to purchase a replacement.
If the screen is black, verify the LCD is functioning by using a flashlight. If you find dim images, the B0101-000776 LED backlight strip may have failed, and/or the 30805-000371 power supply board. Start by inspecting this board closely, as there are two large 68µ capacitors that are prone to fail.
