default or selected kernelversion does not have config value CONFIG_DRM_CLIENT_SELECTION.
Result is shown for kernelversion 6.6.75

CONFIG_DRM_CLIENT_SELECTION (not configurable)

configname: CONFIG_DRM_CLIENT_SELECTION

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)
└─>DRM_CLIENT_SELECTION
In linux kernel since version 5.4.290 (release Date: 2025-02-01)  
Drivers that support in-kernel DRM clients have to select this
option.