@dvl I found this. https://www.reddit.com/r/homelab/comments/tcp2rz/dell_poweredge_r730_boot_from_pcie_m2_device/
It is a disaster of a set of instructions, and I doubt you need all of it. Some of the takeaways that seem to be important in my researching is that you may need to use GPT and UEFI booting if you haven't tried it yet, and you may be able to get UEFI/option rom 'platform firmware' for the SSD itself, thus it won't need BIOS support to boot it will have its own firmware.
@dvl If you need assistance with FreeBSD UEFI/GPT boot I can help, I am an expert here, I wrote my own FreeBSD UEFI secure-boot setup :)
@david Thank you, yes, I also found that. The interesting bit, it seems to be double booting. You need a USB drive to boot clover[1], which then boots your NVMe.
One of the comments says "just one more thing that could cause issues down the line" - if I can avoid it, I will. Which pushes me towards SSD mounted on a PCIe card, which also gives me hot-swap.
Not 100% sure yet. Still reading.
[1] - https://github.com/CloverHackyColor/CloverBootloader/releases
@dvl double booting from USB stick 🤮 I hadn't followed closely enough that, I though that was just to do an update step, not a forever thing
@david I also found this other mention of Clover with Windows.
https://www.tachytelic.net/2020/10/dell-poweredge-install-boot-pci-nvme/
@david one would like to think so.