Or is it a question of budget? If that’s the case, what about a used server (like those from UNIXSurplus)?
Or is it a question of power? If that’s the case, then... I don’t quite know in that case.
Without getting into questions of possible security implications/perceptions of where servers are designed and manufactured... I do like the simplicity of some of the Supermicro options. I currently have a short-depth 1U Atom-based one, which runs passively-cooled except for the PSU fan, which I've replaced with a soldered-in practically silent Noctua. I intentionally got a mobo without a crazy BMC with IPMI, but I still don't assume the hardware is very trustworthy. It might still be more trustworthy than a popular consumer board.
(BTW, if you're looking at any quiet/cool-running server that uses an Intel Atom C2xxx or some other Atom models, make sure that either it isn't a lemon one, or it has a mitigation. [1][2]
[1] https://www.servethehome.com/intel-atom-c2000-avr54-bug-stri... [2] https://www.eevblog.com/forum/microcontrollers/intel-atom-c2...
Not ARM-based though, but they do have a variant that can host 4 pico-itx boards: http://www.casetronic.com/corporates/42-t1040.html . I gather you may be able to convert that one easier to fit an ARM board, or RISC-V for that matter.
Thank you for linking that.
http://www.istarusa.com/en/istarusa/products.php?model=EA-1M... (love the "XServe" aesthetic)
http://www.istarusa.com/en/istarusa/products.php?model=U-140...
http://www.istarusa.com/en/istarusa/products.php?model=M-140... (extra short!)