Data server. U2 connections

I was thinking the Ryzen Threadripper 7945WX (or equivalent 5000WX) Pro (smallest, 12 core) might make a great platform for a data server. The motherboards don’t have many u2 connections though (only one slimSAS). With 128 PCIe lanes I should be able to drive around 20 x4 NVMe drives. But how do I connect all the drives to the board? Are there dedicated u.2 expansion cards? Do I use 4x m2 x16 cards and m2 to u2 cables? I am interested in connecting it eg with some 100Gb/s connection to another server for deep learning.