default or selected kernelversion does not have config value CONFIG_MOSTCORE.
Result is shown for kernelversion 6.7-rc3

MOST Core

modulename: mostcore.ko

configname: CONFIG_MOSTCORE

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>MOST driver
└─>MOST Core
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Say Y here if you want to enable MOST support.
This device driver needs at least an additional AIM and HDM to work.

To compile this driver as a module, choose M here: the
module will be called mostcore.

source code: