You could use something like
P411W-32P (NVMe switch) ( check @aBav.Normie-Pleb thread A Neverending Story: PCIe 3.0/4.0/5.0 Bifurcation, Adapters, Switches, HBAs, Cables, NVMe Backplanes, Risers & Extensions - The Good, the Bad & the Ugly )
or
Adaptec - Adaptec HBA Ultra 1200p-32i (Tri-Mode HBA with internal PCIe switch, NVME drives will be exposed as scsi drives to OS)
They are 16x PCIe 4.0 cards and allow to connect more than 4 NVME SSDs.
I don’t have any Micron U.3 NVME drives yet to test if you can run it in 1x, 2x lane mode.