CONFIG_BINFMT_ELF32 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
default or selected kernelversion does not have config value CONFIG_BINFMT_ELF32.
Result is shown for kernelversion 6.9.9

CONFIG_BINFMT_ELF32 (not configurable)

configname: CONFIG_BINFMT_ELF32

Linux Kernel Configuration
└─>BINFMT_ELF32
In linux kernel since version 2.6.12  
selects
CONFIG_ELFCORE