This is a custom form factor Laptop with motherboard, PSU all being proprietary form factor. So, don't buy this and expect this to be turned into a Decent gaming PC of whatever.
Technically you can add a Graphics card on this, a low profile half height card will fit. But because of the lower capacity PSU, make sure that is a 60W TDP or below card, not a 75W TDP card which can run on PCIe power without external connection. A GT 1030, or some custom RX 450 or 550 should work.