Put a GTX 1080 ti and let us see the definiton of bottleneck
Me neither. But when you look at specs (and name) it has a G31 chipset, so the iGPU is supported by new OS, so it should work without any problems except, obviously, performance.
This thing probably is one of those models that were made to be sold as replacements, similar to "new" 775 motherboards that you can find for 60-70 $ in shops so the fun thing is that OP might have untouched boxes as they are probably leftovers