65in TV Bright/Washed Out/ Bleached Screen - Main Board or Panel?

I have a Samsung 65" UN65KU650DF curved TV (2017) and the screen has just completely washed out. Prior to that 2 vertical lines appeared on the screen for a couple of days and in a week or so the entire screen looks super bright/washed out and bleached (see included image).
Reading online, it looks like it could either be a main board or a panel issue. As far as I understand, there is no separate TCON board on this model.
I have found the exact replacement board (BN94-10828C) on eBay but the seller says that its very likely that this is a screen issue and not a board issue. I have removed the back panel and to be honest the main board looks fine to me with no obvious signs of damage (picture included below).
I can try the replacement board but have no idea on how to diagnose a panel issue or where to even begin.

Any thoughts on what I should try ?
Is this problem for these Samsung models indicative of a faulty board that can be replaced ?