@cscs: does this work: install-grub ($976) · Snippets · GitLab?
More or less we check:
cmp -s /efi/EFI/Manjaro/grubx64.efi /efi/EFI/boot/bootx64.efi && fallback_is_same=true
In my case:
sudo tree /boot/efi
/boot/efi
└── EFI
├── boot
│ └── bootx64.efi
└── Manjaro
└── grubx64.efi
4 directories, 2 files