Nes is 240p, I believe. Most new monitors don't support it.Does your TV/Monitor have an option to output at 256p?
Posting this more because you may find it neat rather than cost effective but the RetroTink 5X can do downscaling to 240p. RetroRGB shows this off with Cave Story and Mega Man 9 around 21 minutes here .
Well I was gonna use dolphin ._.Does your TV/Monitor have an option to output at 256p?