I got a Hyper M.2 x16 card and on my Strix z390F, I can get 2 M.2 cards working on it if I install it on to PCIEx16_2 slot (middle one). This is expected as the manual says the lanes are in 4+4 configuration.
Just to check I connected it to the PCIEx16_3 slot which as only provide 2 or 4 lanes via the motherboard rather then CPU, but one M.2 works and provides similar performance for 2 lanes or 4 lanes. M.2 is intel 660p, so not the fastest, but basically means 2 lanes can provide the bandwidth required.

So just wondering, is there a way to Split the 4+4 lanes on middle PCIE slot in to 2+2+2+2 configuration so I could use all 4 M.2 slots on the Hyber M.2 card?

Thanks,