technical yes. but doesn't mater. My cpu has a onboard GPU. i run it in headless mode.   the error "attempted double use of PCI Address error" means that something else is using the virtual slot 2 for a device so 2 is out. i would move back to 4 or 7...   I would need the entire xml file to assist further. via ubuntu ssh if you use lscpi do you see it in the list. If unraid sees the 3090 via lspci -v what driver is in use. the nvdia card needs to be stubbed a