Comment # 15 on bug 1220276 from Lukas Ocilka

Michael, I've just reproduced the problem without Fedora, but it will be the
same also in a typical scenario: 1st disk: Windows 2nd disk: openSUSE.

My system has three disks: 1. NVME 2. SSD 3. USB

- When I install the first system the installed GRUB obviously sees only that 
  first system only, this will be the case with Windows

- When I install another system, be it openSUSE TW onto the second disk, then
  GRUB at the second disk will see both, the system on the first disk and the 
  system on the second disk

- The same with installing on the third disk, that one sees all three

The problem is that the boot disk is always the first disk (NVME) and then it
always automatically boots only from the first disk making selecting other
system impossible. The only way is to manually change the booting disk in BIOS,
I do that while booting.

I was using Agama for these tests, but that one uses YaST Bootloader under the
hood. Each installation has their own /boot/efi by default.