CONFIG_ARM64_SSBD is not available for the default architecture x86.
Result is shown for architecture arm64
default or selected kernelversion does not have config value CONFIG_ARM64_SSBD.
Result is shown for kernelversion 5.9.9

Speculative Store Bypass Disable

modulename: ssbd.ko
configname: CONFIG_ARM64_SSBD

Linux Kernel Configuration
└─> Kernel Features
└─> Speculative Store Bypass Disable

This enables mitigation of the bypassing of previous stores
by speculative loads.

If unsure, say Y.

source code: