it is a question of cards vBIOS.I tried some old radeon videocards (old ones without extra powersupply) before. they wont work.
some tried GT710/740 with no video, after flashing some vBIOS it worked (don't know which)
so it need some UEFI support and must be signed right way.
on a good picture of this Naples olympus board i see a Gigabyte GV-R523D3-1GL rev. 2.0 (Radeon R5 230)
i have tried a AMD Radeon R5 430 (Dell) but did not work for me.