My LG S43 laptop has dual-boot Windows 10 (upgraded from Windows 8) and Ubuntu 18.04.5 LTS. It worked fine for 2 years, but recently I decided to open it up to clean the fan and replace the thermal paste.
Once opened, I noticed that the LCD cable seemed to be glued on to the metal cover of the fan, so I had to carefully remove it, and also disconnected it from the motherboard.
After the clean up, I reassembled everything and, to my surprise, it worked. I could boot into both Ubuntu and Windows just fine. I was using it for about a week with no problems, when suddenly while I was watching a YouTube video, the screen faded to black, with the backlight remaining on.
Rebooting took me to the GRUB, and booting into Ubuntu took me to the same black screen. I can login by pressing Enter once and typing my password blindly. Switching to tty3 works as well, and when I switch back to tty2 I get a quick glimpse of my desktop. I tried using some keyboard shortcuts blindly like opening a terminal window, but when I caught a glimpse again nothing was open.
Booting into Windows is about the same, I can see the loading screen, but after that it's all black.
I followed some suggestions on this post, such as replacing quiet splash with nomodeset on the GRUB, which lead to the same black screen, and installing Boot-Repair, which when I try to run it on tty3 gives me the error xhost: unable to open display "", I assume because it can only run a GUI. I also went into Recovery Mode and updated the GRUB, no luck there either.
So my question is, what further troubleshooting steps can I take? I could reinstall Ubuntu, but how could that be the root of the problem since Windows isn't working either? I could open it again and mess with the LCD cable some more, but how is that the problem if the screen works for text-only interfaces? It could be a driver issue, but how come if my laptop has built-in graphics and it worked fine for a week?
Any suggestions would be great and I'm happy to answer any questions. Sorry if the formatting is wrong, this is my first question.
edit: I plugged in an external monitor and everything works. Must be something wrong with the screen cable (which I messed around with as mentioned above). If anyone is having a similar issue I'd suggest testing on an external monitor first before messing around with software. What still bugs me is that I can see the GRUB and the backlight works, so the screen is not totally dead. Any suggestions on what to do are still welcome. Will look around some more before taking it to a shop.
