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

Enable secure boot support

modulename: opal-secvar.ko

and/or

plpks-secvar.ko

and/or

secure_boot.ko

configname: CONFIG_PPC_SECURE_BOOT

Linux Kernel Configuration
└─>Kernel options
└─>Enable secure boot support
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
Systems with firmware secure boot enabled need to define security
policies to extend secure boot to the OS. This config allows a user
to enable OS secure boot on systems that have firmware support for
it. If in doubt say N.

source code: