I am currently running a 8 4TB NVMe NAS via OpenZFS on TrueNAS Linux. It is good but my box is quite large. I made this via a standard AMD motherboard with both built-in NVMe slots as well as a bunch of expansion PCEi cards. It is very fast.

I was thinking of replacing it with a Asustor FLASHSTOR 12, much more compact form factor and it fits up to 12 NVMes. I will miss TrueNAS though, but it would be so much smaller.