Hi,
I have a 2017 Lenovo ThinkCentre M800 that I'm using to try to install Arch on a hard drive. I've formatted the drive (under Arch, using fdisk, with gpt partition, etc.), gone through the installation up to the point where I run grub-install with this command: grub-install --target=x86_64-efi --bootloader-id=grub_uefi --recheck
what device did you use for installing? Did you select "Boot UEFI"? Is "BIOS Legacy"-mode enabled in BIOS?
Regards Bjoern