AMD GPUs do not require I/O BARs, and highly doubt Nvidia ones do either. The VBIOS will probably assume it can use it, but most modern cards can be initialized

AMD GPUs do not require I/O BARs, and highly doubt Nvidia ones do either. The VBIOS will probably assume it can use it, but most modern cards can be initialized without actually running the VBIOS (because people use them on headless servers, for virtualization, and things like that). The I/O BAR is only required for legacy VGA compatibility, you can ignore it.