DON'T UPDATE THE FIRMWARE OR YOU'LL BRICK YOUR DINGOO!!!!!!
Dingoo has changed the LCD controller. Before it was an ILI9325, now is an ILI9331_3 (you can check your model with the hidden menu link ) so the unbricking tool won't work.
Sofia should be contacted so they can release a new unbricking tool. btw, current linux won't work on those new models.