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

Include in-kernel firmware blobs in kernel binary

configname: CONFIG_FIRMWARE_IN_KERNEL

Linux Kernel Configuration
└─>Device Drivers
└─>Generic Driver Options
└─>Include in-kernel firmware blobs in kernel binary
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
Various drivers in the kernel source tree may require firmware,
which is generally available in your distribution's linux-firmware
package.

The linux-firmware package should install firmware into
/lib/firmware/ on your system, so they can be loaded by userspace
helpers on request.

Enabling this option will build each required firmware blob
specified by EXTRA_FIRMWARE into the kernel directly, where
request_firmware() will find them without having to call out to
userspace. This may be useful if your root file system requires a
device that uses such firmware and you do not wish to use an
initrd.

This single option controls the inclusion of firmware for
every driver that uses request_firmware(), which avoids a
proliferation of 'Include firmware for xxx device' options.

Say 'N' and let firmware be loaded from userspace.