Is it helpful to exclude the kernel debugging symbols? How to build a firmware with the smallest size ?
https://openwrt.org/playground/faq/which_packages_can_i_safely_remove_to_save_space
https://openwrt.org/playground/faq/build_image_for_devices_with_only_4mb_flash
https://openwrt.org/docs/guide-user/additional-software/saving_space