No audio on MacOS installed on Dell Precision T8510 with Intel C610/X99

[guff666]

I have a Dell Precision T5810 workstation with Proxmox 7.1 installed. This has an Intel C610/X99 series chipset with the associated HD Audio Controller.

I have successfully installed MacOS Big Sur on this using openCore with the video card passed through. However, I cannot get audio to work, either using the onboard device or with USB connected Harmon-Kardon soundsticks. Regardless of how I approach this, MacOS sees no audio devices. I have tried:

• All combinations of adding the Proxmox audio controller
• Passing through the audio controller PCI card
• Passing through the Soundstick's USB port.

If I passthrough the entire USB controller to which the Soundsticks are connected, MacOS does see the device, but no sound emerges.

I'm guessing this is down to one or more of:

• missing kext for the card
• failing to blacklist a module

Any ideas of where to go?