CONFIG_DEBUG_NETX_UART is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_DEBUG_NETX_UART.
Result is shown for kernelversion 6.9.9

Kernel low-level debugging messages via NetX UART

configname: CONFIG_DEBUG_NETX_UART

Kernel low-level debugging port
└─>Kernel low-level debugging messages via NetX UART
In linux kernel since version 4 (release Date: 2015-04-12)  
Say Y here if you want kernel low-level debugging support
on Hilscher NetX based platforms.