default or selected kernelversion does not have config value CONFIG_MLX5_TLS.
Result is shown for kernelversion 6.8.7

Mellanox Technologies TLS Connect-X support

configname: CONFIG_MLX5_TLS

Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>Ethernet driver support
└─>Mellanox Technologies TLS Connect-X support
In linux kernel since version 5.1 (release Date: 2019-05-05)  
Build TLS support for the Connect-X family of network cards by Mellanox
Technologies.