Yes please, I'm facing the same issue.6 month update, just in case anyone is interested.
I'm unsure if a change in Proxmox 7.0 has helped or if I've just gained more experience, but I am now able to passthrough the Intel iGPU with display output on the DisplayPort using GVT-d to a macOS VM.
I have the physical display out and remote access via NoMachine's NX protocol. If a keyboard and mouse is passed through I could utilise the VM as a stand alone workstation.
Anyone interested reply to this and I'll post my config.
DerekG
Thanks!