CONFIG_PSERIES_PLPKS is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Support for the Platform Key Storage

modulename: plpks.ko

configname: CONFIG_PSERIES_PLPKS

Linux Kernel Configuration
└─>Support for the Platform Key Storage
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
PowerVM provides an isolated Platform Keystore(PKS) storage
allocation for each LPAR with individually managed access
controls to store sensitive information securely. It can be
used to store asymmetric public keys or secrets as required
by different usecases. Select this config to enable
operating system interface to hypervisor to access this space.

If unsure, select N.

source code: