99% of Intel mini PCs don’t support ECC unless it’s a Xeon (which is very rare)
For AMD mini pcs, 5700u/5800u/5825u support ECC but i don’t know of any that have 4 NVMes
A decent amount of the newer AMD CPUs (Zen 4) support ECC but the mini pc manufacturer has to enable ECC but afaik none of them do (they’ll try to deceive and say it’s ecc capable because DDR5 has built in ECC, which is not the same)
This newly announced minipc supports 4 NVMes and might support ECC, but you won’t know until it’s out and people test it
But i haven’t known minisforum to support ECC in any of their mini pcs, and even their AMD motherboards but this might be possible since it uses socketed desktop CPUs (7000/8000/9000)
Your best bet is just getting a mini itx Ryzen 7000 AMD motherboard, as a decent amount support ECC memory
Edit:
Or Asrock Deskmeet x600 which supports 4 ECC Dimms and a 4.0 X16 slot(hopefully it supports bifurcation for a 4 x m.2 nvme card)
I’m considering using the new AMD Epyc 4004 platform and building one myself in a not-the-smallest box, but something like this (there are other similar cases):
Silverstone ML03
Then a micro-atx server motherboard (Asrock works for that).
Then at least the fans can be customized so they are silent.
The only thing I don’t know is if those asrock boards have remote console like HPE ILO or if it’s just dumb IPMI for on/off/status?