Titan GT80 not booting off a clone drive 2.5" SSD

I think the real question, has anyone been able to put an operating system on a GT80S SLI model on the non-PCIE/NVMe drives (SATA) and successfully boot?

Either the 2.5" SSD or the 2280, both SATA?

I realize the older GT80 was all SATA and booted just fine of course, but was in UEFI mode or Legacy?

 

Just as an update, I installed Fedora Linux on the 2280 M.2 SATA drive (Not on one of the PCIe/NVMe 2280s) or the 2.5" SATA and it boots.

I had a hard time configuring it in the UEFI boot entry with bcdedit and will try to do so with Grub on the Linux end. But yeah, it boots and though it does not solve the original problem, I will just allocate the 2.5" SATA SSD to data storage so that question is resolved that way.

MSI GT80 SLI 6QE model can have 3 bootable drives and all are 2280 format: M.2 PCIe number one, M.2 PCIe number two, and the third is M.2 SATA (non-PCIe) 2280.
The forth drive in the machine, the 2.5" SATA one, which used to be an HDD as it came from MSI and since upgraded to SSD, apparently cannot be a bootable device no matter what you do. I don't know if it's different on the original GT80 which was all non-PCIe, just SATA.

I am surely not going to swicht from UEFI to Legacy or anything.