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

CONFIG_RADIX_TREE_MULTIORDER (not configurable)

configname: CONFIG_RADIX_TREE_MULTIORDER

Linux Kernel Configuration
└─>Library routines
└─>RADIX_TREE_MULTIORDER
In linux kernel since version 4.1 (release Date: 2015-06-21)  
is depended by
CONFIG_ZONE_DEVICE