CONFIG_PGTABLE_3LEVEL is not available for the selected architecture x86.
Result is shown for architecture loongarch

CONFIG_PGTABLE_3LEVEL (not configurable)

configname: CONFIG_PGTABLE_3LEVEL

Linux Kernel Configuration
└─>PGTABLE_3LEVEL
In linux kernel since version 5.2 (release Date: 2019-07-07)