CONFIG_X86_USER_SHADOW_STACK is not available for thedefaultarchitecture x86.
Result is shown for architecture 64BIT

X86 userspace shadow stack

modulename: shstk.ko

configname: CONFIG_X86_USER_SHADOW_STACK

Linux Kernel Configuration
└─>Processor type and features
└─>X86 userspace shadow stack
In linux kernel since version 4.14.327 (release Date: 2023-10-10)  
Shadow stack protection is a hardware feature that detects function
return address corruption. This helps mitigate ROP attacks.
Applications must be enabled to use it, and old userspace does not
get protection "for free".

CPUs supporting shadow stacks were first released in 2020.

See Documentation/arch/x86/shstk.rst for more information.

If unsure, say N.