Rian Kelly

The reason your 2080 is not selectable for binding is that IOMMU Group 2 contains other devices alongside the GPU. For VFIO passthrough to work, you need to bind the entire IOMMU group to vfio-pci, and Unraid won't let you bind a group that includes critical system devices (like the root port or other PCI bridges).
Two approaches:
1. ACS Override (quick fix): Go to Settings > VM Manager and set "PCIe ACS Override" to "Both" or "Downstream". This tells the kernel to treat each device as its own IOMMU group, splitting up the shared group so the GPU can be isolated. After applying, reboot and check System Devices again. The 2080 should now appear in its own group and be selectable.
The trade-off: ACS override reduces IOMMU isolation guarantees. In a home lab this is fine, but it means devices in the split group could theoretically DMA into each other's memory. For a home GPU passthrough setup this is a non-issue in practice.
2. Physical slot change (cleaner fix): If your motherboard has multiple x16 slots, try moving the GPU to a different PCIe slot. Different slots often land in different IOMMU groups depending on your chipset layout. Some slots connect through the CPU directly (cleaner grouping) while others go through the chipset (shared groups).
Check which devices share Group 2 by looking at the System Devices page. If it is just the GPU plus its audio function (NVIDIA audio), that is normal and both should be bound together for passthrough.