How do you connect the drives? Looking at specs there’s only one sata port (which I don’t actually see anywhere, but it says it is there, although using it slows the second nvme lane)
USB connected drives in a raid array are not ideal. USB connectivity is not as solid as a direct sata connection and a drive suddenly disappearing from your area, especially parity, is quite a headache
No pci slot so you can’t add an hba for more sata lanes either. You could do one of those nvme to sata things but I’ve heard bad things about the reliability of those.
If it’s free though I def think it’s worth finding a way to make it work. The specs are more than enough for unraid and usually those tiny pcs are pretty power efficient, which is nice. But that’s the issue to work around, connecting the hard drives reliably.
WRT what to put them in it could be anything really. You could get a cheap broken 1 or 2u server case where someone’s pulled the motherboard and powersupply, rig something in there to hold them all. Should be more than enough space for 5 drives and will probably have cages for at least 2-3, maybe all 5 if you get lucky. Might even have hot swap ones. Dunno if this would fit though, that rack looks small and I couldn’t get the specs to load, is it full sized or a tiny one?
Could also see if there’s some kind of 3d print thing. There’s probably a 3d print thing to rack mount that mini pc.