When using U-Boot with UEFI and Grub, you don’t need any patches, only an updated recipe.
But upgrading U-Boot may also solve the ARM64 Image magic problem, so I encourage you to try both configurations: One with mender-grub turned on, and one with mender-uboot turned on. For mender-uboot you will indeed need patches, but sometimes the existing ones keep working even when upgrading; it’s hard to say in advance.