I'm looking at four 3.5" spinning drives + an m.2 for boot.
There are two boards that I'm looking at. This first one is very similar to the one posted earlier, it uses a 4-pin DC input or a 24-pin ATX:
Board Manual
The second is a newer board but they want an 8-pin ATX + 4pin sense that seems to adapt from the 24-pin?
Board Manual
I would prefer the second board but it looks much more complicated to get working. How does the PCDB board give 5V for the drives? What parts would I need to make these work?
Also here's an image of the Dell DA-2 with its pinout: