default or selected kernelversion does not have config value CONFIG_DISCONTIGMEM.
Result is shown for kernelversion 6.9.9

CONFIG_DISCONTIGMEM (not configurable)

modulename: numa.ko

and/or

discontig.ko

configname: CONFIG_DISCONTIGMEM

Linux Kernel Configuration
└─>Memory Management options
└─>DISCONTIGMEM
In linux kernel since version 2.6.12  
source code:
arch/alpha/mm/numa.c