Klopstock

I think his biggest problem is package installation for which he can use discover or his equivalent for his de.

I personally had the best experience with mergerfs (Drives can be any size and can be backuped by snapraid) and an external enclosure up until recently. Unfortunately USB is such a limiting factor because of bandwidth and also latency. I can only realy recommend to get a new cheap Server which has Support for sata If you want any usability while Transferring or moving files.

I personally would recommend this n100 to get a real psu which can add many drives, 6 Sata ports and a standard form factor.

Edit: Also a PCIE Slot to add 10 Gbit Networking Card if dual 2.5gbit is too slow. And if you need more power there is also and i3 n305 variant of these mainboards.