CONFIG_ADB_KEYBOARD is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k
default or selected kernelversion does not have config value CONFIG_ADB_KEYBOARD.
Result is shown for kernelversion 5.4.123

Support for ADB keyboard (old driver)

configname: CONFIG_ADB_KEYBOARD

Linux/68k Kernel Configuration
└─>Character devices
└─>Support for ADB keyboard (old driver)
In linux kernel since version 2.6.12  
This option allows you to use an ADB keyboard attached to your
machine. Note that this disables any other (ie. PS/2) keyboard
support, even if your machine is physically capable of using both at
the same time.

If you use an ADB keyboard (4 pin connector), say Y here.
If you use a PS/2 keyboard (6 pin connector), say N here.

depends
CONFIG_MAC
NOT CONFIG_INPUT_ADBHID