For the mobo to recognise the m.2 SSD via PCIexpress card you need a hacked BIOS that allows that capability.
A few threads back, there is a how-to, but it is simply as doing a BIOS upgrade as any other.
Hacked BIOS that works with my Samsung 960 EVO m.2 nvme SSD is attached. No guarantees.
I updated clover from 4359 to 4617 and then tried to update to 10.13.6.
The system stopped booting. I rebooted into a 2nd drive with old clover, booted into the system and re-ran multibeast to restore clover to 4359. The system then updated correctly.
It boots a bit slow now, I assume it is the "emulated NVRAM" option I chose. I will do it one more time without this option and see how it works.