default or selected kernelversion does not have config value CONFIG_BINFMT_SHARED_FLAT.
Result is shown for kernelversion 6.9.9

Enable shared FLAT support

configname: CONFIG_BINFMT_SHARED_FLAT

Linux Kernel Configuration
└─>Executable file formats
└─>Enable shared FLAT support
In linux kernel since version 2.6.12  
Support FLAT shared libraries