With APUs, you must buy the Pro SKUs for ECC support. I specifically had to get the 5650g pro (as opposed to the regular 5600g) for my home server due to this exact reason.
Just curious, but why opt for an apu in a server config? They tend to be marketed towards gamers on a budget so not including ecc support isnt that big of a deal.
Still need video output to set up the system and for occasional maintenance. Additionally, I host a media server that needs to transcode videos. The GPU in the APU is perfect for these tasks since it both costs less and draws less power than a discrete card.