Step-by-step – Kernel 5.13 From Source Installation in Debian Buster

Configuring

5. 5. Configuring Kernel

   So now to Configure Debian Custom Linux Kernel
   First, access the Kernel Source with:

   cd linux*

   Then copy the current Configuration File into the New Kernel Source:

   cp /boot/config*`uname -r` .config

   In case of a Chrooted System instead you may look up the available Kernels with:

   ls /boot | grep config

   The grep Command refine the output List showing only the entries Matching the Keyword.
   Again fix the Configuration File editing it with nano and commenting out like:

   sudo nano .config

   Use Ctrl+w to search for “CONFIG_SYSTEM_TRUSTED_KEYS” on nano.
   And comment out the Line like:

   #CONFIG_SYSTEM_TRUSTED_KEYS="debian/certs/debian-uefi-certs.pem"

   Ctrl+x to Save & Exit.
   Else to make a Custom one then reconfigure the Kernel (Only for advanced Users) with:

   sudo make menuconfig

   For instructions see: How to Configure a Build Kernel.