If you want a lot of NVMe sockets, my recommendation would be the Lenovo M920x. It has 2 on board. Then you can add a special riser card, which gives you 2 more + a 8x PCIe slot.

Which gives you 4 NVMe slots + SATA + one 8x PCIe slot and not counting the B-Key WiFi slot which also has PCIe.