it seems that DP-port issues (black screen) remain, when employing the respective Vega SSDT PCI device implementation on Sapphire Nitro+ Vega 64 (2x HDMI, 2xDP) or ASUS Strix Vega 64 (2x HDMI, 2x DP, 1x DVI) GPUs, which only can be removed by adding Whatevergreen.kext v.1.2.2.