and NVMe SSDs: What are they and how do they benefit your PC?

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:

Reviewing the AMPCOM NVME SSD to PCIe Adapter Card, 64Gbps SSD X4

pcie m2 slot Reviewing the AMPCOM NVME SSD to PCIe Adapter Card, 64Gbps SSD X4

pcie training error slot 1 2 drives are “keyed” at one end so as to prevent the end-user from inserting them in an incompatible socket PCIe NVMe drives are 'M' keyed SATA ones,