Some of the newer machines don't look for anything other than the Microsoft folder in EFI. Instructions for ubuntu are similar for others.

    mount /dev/sda1 /mnt
    cd /mnt/EFI

    mkdir -p Microsoft/Boot
    cp /mnt/EFI/ubuntu/grubx64.efi /mnt/EFI/Microsoft/Boot/bootmgfw.efi

You may also need to create /EFI/Boot and copy the .efi file there as well.