CONFIG_UML_PCI is not available for thedefaultarchitecture x86.
Result is shown for architecture um

CONFIG_UML_PCI (not configurable)

modulename: virt-pci.ko

configname: CONFIG_UML_PCI

Linux Kernel Configuration
└─>UML_PCI
In linux kernel since version 5.4.295 (release Date: 2025-06-27)  
source code:
arch/um/drivers/virt-pci.c