default or selected kernelversion does not have config value CONFIG_SLUB_DEBUG.
Result is shown for kernelversion 6.9-rc7

Enable SLUB debugging support

configname: CONFIG_SLUB_DEBUG

Linux Kernel Configuration
└─>Kernel hacking
└─>Memory Debugging
└─>Enable SLUB debugging support
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
SLUB has extensive debug support features. Disabling these can
result in significant savings in code size. While /sys/kernel/slab
will still exist (with SYSFS enabled), it will not provide e.g. cache
validation.