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

CONFIG_UML_IOMEM_EMULATION (not configurable)

configname: CONFIG_UML_IOMEM_EMULATION

Linux Kernel Configuration
└─>UML-specific options
└─>UML_IOMEM_EMULATION
In linux kernel since version 4.14.326 (release Date: 2023-09-23)