[Solved] How can I boot a NVMe drive if the bootloader can't see it?

[gluhend]

I have Debian installed on a sata ssd drive on my ThinkServer TS430 (Xeon E3-1220v2). I wanted to move it to a NVMe drive (m.2 on a PCIe adapter) and have used gparted to copy it to the drive (and changed the uuids and updated fstab), but the computer's firmware is unable to recognize it as a boot option and it simply doesn't show up. Rescatux can see the drive and when I choose "fix bootloader" it can see the OS and the NVME drive, but does not list the NVME drive as a possible one to install the bootloader to.

So far it seems that I'll need to use a second boot drive. I don't want to use the old SSD as I'd like to leave it untouched in case the nvme drive doesn't work, then fully reformat it for use. none of the other drives are visible in the bootloader as they are on a PCIe drive controller.

I'd like to use a USB drive, and the ideal one I have is a 16GB Cruzer Fit that sits flush with only a tiny stub sticking out of the port. I'd like to figure out how to install grub to it to autoboot the NVME drive, additionally I'ld like to add some partitions with tools like rescatux, rescuzilla, Debian netinstall, and netboot.xyz that the grub bootloader has as options if I cancel the autoboot.

How would I set up the grub bootloader and it's partition? And can I do this from a different computer so I don't have to take the server offline until the bootloader is ready? And should I use Grub2 or rEFInd or Clover or OpenCore or Ventoy or something else?

[gluhend]

Update: I figured I could save a headache by doing a clean install of Debian and do housekeeping while I'm at it. put a efi and a /boot partition on the sandisk drive and everything seems to work
Update2: migrating the apps for the server has been a headache but a much, much smaller one.

[Northpoint]

Good to read that you got a game plan figured out.

I bought a PCIe adapter for 2 NVme's a while back only to discover that it didnt have boot capabilities. I had to reorder another adapter instead.

[Aki]

@gluhend:
Please, mark the discussion as "solved" manually adding the text tag "[Solved]" at the beginning of the subject of the first message (after other tags, if any); i.e. : [Software][Solved] How can I boot a NVMe drive if the bootloader can't see it?

Happy Debian !