Yes I've been here before. I’ve unknowingly purchased laptops with hidden liquid damage and a bad past. Once I seen that and how severe it was before cleaning, I abandoned the rebuild attempt to avoid any future issues I'd probably need a new unit for anyway and make sure nothing is going to kill the new machine - yes the risk of a sudden issue I can't work around is low when it's used where I can chance it, but my time is also worth more then having to hope it's reliable.
That said, the replacement unit has no such issues, and was incorrectly advertised with a lesser CPU then it actually has :-). I thought I at least found a 1:1 unit, but the seller listed it as an 8250U unit when it really has an 8350U - SCORE! I also checked out the screen it has - LGD0557 (FHD IPS, LG) - double score :-). The LG LCD is the one you want, although the BOE/AUO LCDs aren't bad either if you get it. How sad do you think I am the bad unit is a total loss knowing what I replaced it with? Yeah, no.
I mention this as a prime example of how I got burned. Yes, I can fix water damage. The issue is the long term effects, especially with more corrosive liquid. If it want such a sneaky bastard that comes fatal failures when left to sit for who knows how long before it comes back to bite you (especially “mystery” spills, though I suspect coffee), I'd have tried if it wasn't for the damage done and potential hidden issues like UHS damage, especially since the ZIF sockets were affected too - including the trackpad which controls the keyboard and trackpad.
Between the liquid damage and messed up history, and the fact I may need to replace the USH PCB (cables have to be, no way around that). Oh, and there may be permanent damage that needs repair or a replacement motherboard the unit is a total loss since it's so suspect. I might try one day, but I'm not buying parts for it. If I get a decent amount of RAM and can free up a low value SSD I may fix it, but otherwise it's not a machine I'd put money into.
Sadly, you got burned the same way :(. Unless you can source a new board or know someone who can replace the LCD connector, you’re screwed since you bought the computer “as-is”. See if you can find a cheap motherboard, or try your hand at microsoldering since you have nothing left to lose if the board is potentially trashed to the point it needs to be replaced and you can’t even find a shop who can take online repairs to do it.
Next time, assess the unit before ordering parts so you don’t throw good money after bad - it’ll save you a lot of pain next time. Do you think I regret assessing the laptop a bit before I put money towards it? I found a serious issue which affected multiple areas of the motherboard to the point I ducked and ran.