No.Most of these Adapters provide support for "M" or "B" key M.2 SSDs. Old R710 cant boot from the "M" variant. The B will work BECAUSE you have to wire it up to the onboard SATA port.I have converted a bunch of R510/515 to use M.2 as boot because i need all HDD slots for backup storage.
Hey All, First off thank you for taking the time to read this post. I'm trying to turn my bare metal R710 in a TrueNAS server, but didn't want to sacrifice a SAS device to be the boot device; so I got a NVMe M.2 PCIe adapter. I can install the OS to the NVMe SSD. The issue I'm running into is on reboot BIOS doesn't see the drive so it can't boot into TrueNAS Core. I'm running a SAS Controller, but my adapter is SATA could this be the issue? Any guidance would be greatly appreciated. 
Is the Dell PowerEdge R710 able to boot from a Lycom DT-120 M.2 PCIe to PCIe 
3.0 x4 Adapter (Support M.2 PCIe 2280, 2260, 2242)