Some firmware likes to rewrite the UEFI boot order every time MS Windows’ UEFI loader is found on the UEFI partition. This is the workaround.

Rename the Microsoft directory in your UEFI partition to Windows_10.

Then create a static grub entry in /etc/grub.d/40_custom: NOTE: change the UUID on the search lines to the UUID of your UEFI partition. Mine was 6EB4-4B14. Use blkid to find the partition UUID.

menuentry 'Microsoft Windows 10 Enterprise' --class windows --class os $menuentry_id_option 'osprober-efi-6EB4-4B14' {
  insmod part_gpt
  insmod fat
  set root='hd0,gpt1'
  if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  6EB4-4B14
    search --no-floppy --fs-uuid --set=root 6EB4-4B14
  chainloader /EFI/Windows_10/Boot/bootmgfw.efi

Update grub.conf:

# grub-mkconfig -o /boot/grub/grub.cfg

Then reinstall grub:

# grub-install