DeeJayDemon

Depending on what interface the lcd screen has, you can buy a display driver for it, which takes hdmi or displayport or vga and converts it to that lcd panel's interface.
eBay will have all kinds of such controllers.
 
As for connecting directly to internal connectors, you pretty much have only USB inside. So for example, you could get a raspberri pi or something else with video out and usb and connect the pi to a usb header on the motherboard.
You can write software on the pi to create image and output it to hdmi and then that's sent to the lcd display. Software receives data through the usb connector from a software running on your pc

Check this video out, it's exactly what you're talking about
 
 

Only think i can think of would be desoldering a port then soldering some ribbon wire to the port then the the screen. But i wouldn't risk my Mobo/GPU unless you have a old GPU you can put in the slot below your main GPU and don't care if you f*** it up.

Also it would be cool to have the screen in ur case
 
edit: i just realized it would be in the case before i said that. DONT JUDGE ME

I hope next year instead of a 2050Ti they do a 2060 Ti.... that seems like the shit to me. like... mix it up a bit ffs