

It’s not impossible, but first Gen Ryzen was surprisingly good after AMD shit the bed for a few years. Most major manufacturers weren’t willing to take a chance, though you can find some 2nd Gen available on the used market.
If it were me, I’d look for a motherboard/CPU combo and assemble it into your case of choice. That way you aren’t stuck with the weird form-factors of pre-built office computers.
Jonsbo makes some decent compact nas cases with plenty of space for drives. Look at their N series N3/N4 etc.
matx would be more upgradable than itx, but nobody is making either of them with 10gb Ethernet. So I personally would be looking at full ATX boards so I could add in a nic.