To install PCI-express attached NVME disks in HPE DL380 Gen10 servers one would need to have three components:

Cage for NVME disks, such as this 8SFF bay for 2.5” caddies:

There are some chips for 100 MHz clock distribution and power management, as well as glue logic for LEDs on caddies and hot-swap detection.

Interconnect riser card that to route PCIe lanes from CPUs to cage box

High-speed cables capable to support PCIe Gen3 speeds

Each cable carry 4 PCIe lanes in each direction and support PCIe Gen3 speeds. These cables are manufactured by Amphenol and have white color, unlike usual SAS cables that are teal color in HPE servers.

This kit also require second processor in the system since most of the PCIe lanes are routed to secondary socket.