An improved workaround, add the f2fs.mod to /EFI/ubuntu then put
search.fs_uuid <your efi fs uuid> efs insmod ($efs)/EFI/ubuntu/f2fs.mod
at the top of grub.cfg
An improved workaround, add the f2fs.mod to /EFI/ubuntu then put
search.fs_uuid <your efi fs uuid> efs EFI/ubuntu/ f2fs.mod
insmod ($efs)/
at the top of grub.cfg