It Looks Like PCIe NVMe SSDs Require Bigger Slots

LnkSta shows link Sta tus: PCIe x2 @ 5GTs the ssd in that slot is a PCIe x2 nvme You can get the same information via sysfs : speed:

2 slot You can see two standard slots on the PCB, between the PCIe slots These have the mounting holes for horizontally mounting

pcie slot dimensions Drives that use NVMe were introduced in 2013 to attach to the Peripheral Component Interconnect Express slot directly on a motherboard

pcieslot Your board may have multiple PCIe* slots The PCIe SSD needs a PCI Express* x4 or higher connector Best performance is with a PCIe connector