That nudges you towards a C2x6 motherboard and CPU with iGPU. These typically come with 8 SATA and 2 M.2.
C246: X11SCH with Core i3-8100/9100 (yes, ECC!) or Xeon E-2100/2200. Issue: these motherboards are now hard to find. (Can find AsRock Rack E3C246 on ebay.)
C256: X12STH with Xeon E-2300 (no Core i3). Issue: expensive. Edit: example here.
side option: W480/W580 with Xeon W-1200/1300. Meant for workstation, but Supermicro boards come a BMC as well.
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