CONFIG_ARM64_BTI is not available for the default architecture x86.
Result is shown for architecture arm64

Branch Target Identification support

configname: CONFIG_ARM64_BTI

Linux Kernel Configuration
└─> Kernel Features
└─> ARMv8.5 architectural features
└─> Branch Target Identification support

Branch Target Identification (part of the ARMv8.5 Extensions)
provides a mechanism to limit the set of locations to which computed
branch instructions such as BR or BLR can jump.

To make use of BTI on CPUs that support it, say Y.

BTI is intended to provide complementary protection to other control
flow integrity protection mechanisms, such as the Pointer
authentication mechanism provided as part of the ARMv8.3 Extensions.
For this reason, it does not make sense to enable this option without
also enabling support for pointer authentication. Thus, when
enabling this option you should also select ARM64_PTR_AUTH=y.

Userspace binaries must also be specifically compiled to make use of
this mechanism. If you say N here or the hardware does not support
BTI, such binaries can still run, but you get no additional
enforcement of branch destinations.