iGPU displayport output not working

Hi all

I'm running Ventura (13,1) on a Gigabyte Z390, Core i9-9900K, iGPU-only system. Full build here. The motherboard has one HDMI port and one Displayport. HDMI works just fine in macOS, Windows and Ubuntu. Displayport works in Windows and Ubuntu and I get multi-monitor support. In macOS, only HDMI works. The other port is not detected at all. I have tried:

• Changing SMBIOS from iMac19,1 to MacPro7,1 (found in a reddit post that this helped someone else)
• Adding `igfxagdc=0` to boot-args (again from another reddit post)
• Checking my BIOS settings. There's nothing I can see pertaining to the displayport
• I do already have WhateverGreen on this setup, though I believe it may no longer be necessary. Not certain on that though

Here's my DeviceProperties, if it's relevant. IIRC I tried AAPL,platform-id 07009B3E and got a black screen, so I used the alternative. I could be wrong on that though as I've built a couple of hackintoshes and it's a little hazy.

https://preview.redd.it/2c4ps8jnlj7d1.png?width=543&format=png&auto=webp&s=22b02c5e9718f96645c7162a596fdcc17c095a04

I'm running OpenCore 0.88, which I realise is a little out of date now. This machine is used for live performance and it's rock solid. Just been on tour and I was reluctant to update anything prior. I'm happy to try updating OC if this might be relevant.

Happy to answer any questions or provide any needed info. Thanks in advance :)