I’ve been spending some time with a Zisworks zero-lag / integer scale 4K kit installed in my Samsung monitor. It is a zero-lag (or at least sub 1ms) solution and (when a compatible signal is sent) the integer scaling works perfectly, but unfortunately, it’s not currently stable enough for most classic console gaming. There’s a TON of potential though and many issues might be fixed with just a firmware update.
Please check out the video, but also subscribe and keep an eye on the news pages, as I have a feeling there will be some good updates to this project in the future! Also, for more info, check out an interview below I did with Zis last year!
Main Webpage: http://www.zisworks.com/
Google Group: https://groups.google.com/forum/#!forum/zisworks-x28x39-user-group
Samsung Monitor used in this video: https://amzn.to/2IfHkdc