CentOS 8 kickstart post install snippet to set a grub2 keyboard layout.

keyboard-layout.ks

%post

# Setup grub2 keyboard layout.

KEYBOARD_LAYOUT=at

[ -d /sys/firmware/efi ] \
	&& boot_directory=/boot/efi/EFI/centos \
	|| boot_directory=/boot

# Fix installation of grub2 UEFI modules on x86_64 platform, the installer installs
# grub2-pc-modules and if you explicitly specify to install grub2-efi-modules it
# would install grub2-efi-aa64-modules instead of grub2-efi-x64-modules.
{
	[ "$(uname -p)" == "x86_64" ] && [ -d /sys/firmware/efi ] && {
		dnf install -y grub2-efi-x64-modules
		grub2-install --boot-directory=$boot_directory --efi-directory=/boot/efi
	}
}

cd $boot_directory/grub2

mkdir layouts
zcat /lib/kbd/keymaps/xkb/$KEYBOARD_LAYOUT.map.gz | \
	grub2-mklayout -o layouts/$KEYBOARD_LAYOUT.gkb

CUSTOM_CONF=/etc/grub.d/40_custom

echo "insmod keylayouts" >> $CUSTOM_CONF
echo "keymap \${prefix}/layouts/$KEYBOARD_LAYOUT.gkb" >> $CUSTOM_CONF
echo "terminal_input at_keyboard" >> $CUSTOM_CONF

for config_file in /etc/grub2.cfg /etc/grub2-efi.cfg
do
	[ -f "$config_file" ] && grub2-mkconfig -o $(readlink -e "$config_file")
done

%end