well, you can boot with the vendor firmware, enable the discrete GPU and check in your OS (xrandr, for instance, I guess) where the display is connected.
eDP? That's probably not very helpful to you, I'm sorry. Doesn't that just say that it's an internal connector?
o You'll always use the integrated one to handle displays. PrimaryDisplay = Display_iGFX
And SkipExtGfxScan is disabled?
o You'll most likely have to figure out how to toggle power to the dGPU. This is mainboard specific, can be a GPIO, for instance. So I suggest to boot with the vendor firmware, dump GPIOs, toggle the dGPU, and dump again. With some luck you'll find a GPIO that changes respec- tively. You can find an example of similar code in src/drivers/lenovo/ hybrid_graphics/.
I'll work on this, then.