default or selected kernelversion does not have config value CONFIG_ARCH_K3_J721E_SOC.
Result is shown for kernelversion 6.9.2

K3 J721E SoC

configname: CONFIG_ARCH_K3_J721E_SOC

Linux Kernel Configuration
└─>Device Drivers
└─>SOC (System On Chip) specific Drivers
└─>K3 J721E SoC
In linux kernel since version 5.1 (release Date: 2019-05-05)  
Enable support for TI's J721E SoC Family support