Question Why doesn't my DisplayPort work during POST and GRUB?

[MihailMihov]

I've just moved over to a DisplayPort cable, but it doesn't work during POST(nor after going into the BIOS) and more importantly during GRUB(the bootloader which I use to dualboot Windows 10 and Fedora), so currently I can only get into my Fedora installation. Switching back to HDMI fixes everything. UEFI Fast boot is off, so that's not it.
My DisplayPort is plugged into the GPU.

Specifications:

ASRock Fatal1ty Gaming K6 (Z170 chipset)

Intel Core i7-6700K

MSI R9 290

M.2 NVMe Samsung SSD 950 Pro 256GB

some other SSDs and HDDs, but that should be irrelevant.

My monitor is a Dell P2715Q (4K@60hz)

 

[thbritto]

The post states that this may be caused by the GPU, boot mode, GPU priority etc. They also give some instructions to solve this issue.