default or selected kernelversion does not have config value CONFIG_NULL_TTY_DEFAULT_CONSOLE.
Result is shown for kernelversion 6.6.86

Support for console on ttynull

configname: CONFIG_NULL_TTY_DEFAULT_CONSOLE

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Support for console on ttynull
In linux kernel since version 6.6.86 (release Date: 2025-04-07)  
Say Y here if you want the NULL TTY to be used as a /dev/console
device by default.

For example, it might be useful to prevent a VT-less kernel from
writing the system log to a random device connected to the serial
port.

Another console driver still might get preferred via the command
line, SPCR, or the device tree.

If unsure, say N.