In my undertaking I'm using a CM2009 IC between real VGA controller and VGA output connector. It is really talked about in the datasheet for this IC which i can use EMI filters on HSYNC, VSYNC and DDC channels correct right after IC and in advance of VGA connector. Though https://hudhelmet57542.mybuzzblog.com/10852088/not-known-details-about-emi-testing-lab