CONFIG_LEFI_FIRMWARE_INTERFACE is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
default or selected kernelversion does not have config value CONFIG_LEFI_FIRMWARE_INTERFACE.
Result is shown for kernelversion 6.9.9

CONFIG_LEFI_FIRMWARE_INTERFACE (not configurable)

configname: CONFIG_LEFI_FIRMWARE_INTERFACE

Linux Kernel Configuration
└─>LEFI_FIRMWARE_INTERFACE
In linux kernel since version 3.15 (release Date: 2014-06-08)