I bout a new HDD and installed linux mint. Works fine except for two major things. Related to the post, I cannot get the bootloader to find windows 10 no matter what I do. I might try to swap the windows drive to sata slot 1 and see if that (a) still works for windows and (b) gets grub2 working. For now, I have to go into the BIOS and mess with the boot order there to switch.
The second problem, not related, is there doesn't appear to be any fan control software that works for my MSI motherboard's CPU fan (lmsensors doesn't see any sensors related to it) so the fan constantly runs even when it's fine in silent mode on windows with regard to temperature. I have trouble with certain sounds (and trouble hearing over background sounds in general) so this is actually more of a dealbreaker than the bootloader.