CONFIG_ARM64_AS_HAS_MTE is not available for thedefaultarchitecture x86.
Result is shown for architecture arm64

CONFIG_ARM64_AS_HAS_MTE (not configurable)

configname: CONFIG_ARM64_AS_HAS_MTE

Linux Kernel Configuration
└─>Kernel Features
└─>ARMv8.5 architectural features
└─>ARM64_AS_HAS_MTE
In linux kernel since version 5.1 (release Date: 2019-05-05)  
is selected by
CONFIG_ARM64_MTE