full system spec?
monitor connected to the gpu and not the motherboard output?
Could be a few things. Can you test that monitor on another desktop / laptop / tablet? If it works with something else that's probably not your monitor. You could try running your monitor on your integrated graphics to see if it does the same thing. Could be the GPU. Could be the cable of your monitor. Start the elimination process.
and with the igpu, same issue?
I've tried two different monitors and different HDMI cables and the integrated graphics unfortunately
And? What happened with the other monitors and IGPU? White lines?