Got it working for anyone running Unraid on top of Qemu like Proxmox. I had to download a bios for the P2000 and include in the proxmox config:
https://forum.proxmox.com/threads/amd-gpu-passthrough-issue-windows-10-steps-included.25427/page-2
https://www.techpowerup.com/vgabios/198658/198658
And this is my proxmox config:
bootdisk: scsi0
cores: 2
cpu: host
hostpci0: 01:00.0
hostpci1: 03:00,romfile=nvidia_p2000_bios.rom,x-vga=on
ide2: local:iso/plopkexec.iso,media=cdrom
machine: q35
memory: 15000
name: unraid
net0: virtio=8E:6C:07:3D:FA:D4,bridge=vmbr0
numa: 0
onboot: 1
ostype: l26
scsihw: virtio-scsi-pci
serial0: socket
smbios1: uuid=181e28f6-9cb3-4fd4-82c3-72dc91b6b553
sockets: 4
usb0: host=2-1.2
vmgenid: 138739ff-1cd6-435b-8829-8597432f0e11