CONFIG_GENERIC_BOARD is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin
default or selected kernelversion does not have config value CONFIG_GENERIC_BOARD.
Result is shown for kernelversion 5.13-rc2

Custom

modulename: generic_board.ko

configname: CONFIG_GENERIC_BOARD

System type
└─>Custom
In linux kernel since version 2.6.24.1 (release Date: 2008-02-08)  
GENERIC or Custom board Support.

source code:
arch/blackfin/mach-bf533/boards/generic_board.c
depends
CONFIG_BF531 or CONFIG_BF532 or CONFIG_BF533 or CONFIG_BF534 or CONFIG_BF535 or CONFIG_BF536 or CONFIG_BF537 or CONFIG_BF561