Asus X555L Not detecting its own display

So I have this laptop, it worked wonders for me for a while but I update its Windows 10 Pro firmware through the usual Windows Update function and I had this problem (which started occurring around the 2020 May update) where it would just turn on but it wouldn't display anything on screen.

I had to hook it up via HDMI to a second monitor to ever make it work and I would always just restore to a previous restore point to gain back display functionality. I stopped using it for a while and decided I wanted to sell it. I reset it to factory settings and everything was working fine but before selling it I thought it would be nice to update it and check if the problem occurred to avoid problems with the buyer in the future.

It happened again only now it wouldn't revert no matter what. I've tried everything:

-Updating drivers both through windows and company website. (I also tried installing very first version, no luck).
-Disabling drivers so motherboard would do it for me, no luck.
-Resetting to factory settings again, no luck.
-Reinstalling Windows, no luck.
-Updating the BIOS firmware and Reinstalling Windows, no luck.

It doesn't even show the ASUS brand screen on boot-up. Only on the second monitor and when I try to detect it through the settings panel it just doesn't show up. Its not my screen itself or its connection because the hardware was the exact same until one day ago when I tried updating it. I think I must figure out a way to "install" the connected monitor but I don't know. Any help I'd really appreciate it. I don't wanna let it go to waste, I'm selling it for like 100 bucks but I can't sell it like this, heck I'd even donate it I just don't wanna throw it away!

Tl,DR: Asus X555L can't identify built-in monitor after Windows Update no matter what, help pls!