It is possible to load standard Linux kernels from your distribution on ARM devices like the Raspberry Pi. No need to download binary kernel images from GitHub repsitories or to compile the kernel yourself every time a security issue is fixed.
Instead, you load U-Boot which in turn loads the EFI variant of Grub (from your distributions package repository). U-Boot doesn't require a boot script in that case. You just generate a Grub image and place it in the folder efi/boot of your boot partition and rename the grub image to bootarm.efi. U-Boot will see that file and load it.
The only thing I didn't figure out yet is why Grub cannot load its configuration file. It only boots to its prompt. It seems Grub cannot detect the partitions despite having the part_msdos and the fat module included.
There is also a thread about this topic on the Devuan Forum with more instructions: