I have a D-Sub only monitor connected to the motherboard with HDMI -> D-Sub converter and I have no problems with this setup (running on iGPU). I bought a Gigabyte GTX 1660S GPU and tried to connect my monitor to it the same way, but it doesn't work properly. Past the "Press F2 to get to UEFI" screen the monitor shows no signal and shuts down. I can't get to Windows and can't boot up Windows 10 pendrive. When I try to boot Ubuntu live USB, I can only do it in "graphics safe mode" that sets the resolution to 800x600. UEFI works fine. The GPU works properly connected to a TV with normal HDMI cable. Any ideas? Also I tried to connect three different monitors - one 1080p and two 1280x1024 and none of them worked. I guess the question is what is this GTX outputting, so that no monitor can see it?
That is so odd. I used DisplayPort to VGA passive adapter before with not issues. Those should be cheap.