No Synology build currently has disk support for NVMe devices.  FSxxxx only support SATA/SAS. NVMe slots on DS918+, and M2D17 M.2 SATA slots are only for SSD Cache (show up only as Cache Device, not disk), at least for now. The above is evidence that the hardware is being recognized and the device is working with the driver loaded in extra.lzma.  Just DSM is not seeing it, probably due to /dev/nvme* name and DSM internal scripting for /dev/sd*.  IG88, please keep the nvme module in!