CONFIG_CERT_STORE is not available for thedefaultarchitecture x86.
Result is shown for architecture s390

Get user certificates via DIAG320

modulename: cert_store.ko

configname: CONFIG_CERT_STORE

Linux Kernel Configuration
└─>Processor type and features
└─>Get user certificates via DIAG320
In linux kernel since version 4.14.327 (release Date: 2023-10-10)  
Enable this option if you want to access user-provided secure boot
certificates via DIAG 0x320.

These certificates will be made available via the keyring named
'cert_store'.

source code: