I suppose you can buy one mini pcie to m.2 converter to get nvme drive support, the speed will be limited to 3.0*1 ~1GB/s, a bit higher than sata 3 600MB/s. The form factor for nvme drive will also be limited because of the design of the board, i suppose it would be better to use 2230/2242 m.2 drive. It seems the built in m.2 slot is dedicated for sata m.2 drive and I am not sure will it be repurposed as nvme m.2 slot.
Personally i would not suggest using mini pcie to m.2 converter to get nvme support as the converter adds up instability.
