Hoping someone can shed some light on this issue I'm having with my 2015 rMB.... I have a Samsung 28 inch 4k monitor that works very well using the Apple AV multipart hub and a 2.0 HDMI cable. I get 4k at 30 Hz with all the scalable HiDPI options (see screenshot). I bought another 4k monitor for my office (a 32 inch 4k by AOC) under the assumption it would work just as well. Using the same hub and HDMI cable, I get 4k at 30 Hz but only native resolution. None of the scalable options show. If I "alt" click on the scalable radio button, I only see low resolution options. By using the instructions at this site, I was able to create a 1920x1080 HiDPI option but that's it. I don't get the very helpful and useable options I get on the Samsung (1440 HiDPI in particular). The monitor seems to have the same specs and has both HDMI 2.0 and DP 1.2. I've tried looking at the monitor options but don't see any settings that should effect this (I can change the HDMI port to 1.4 and tried this but it made no difference). Unfortunately, I bought the monitor from a local smaller store and they made a point of telling me that there are no returns! Looks like I'm stuck using native 4k or 1080 HiDPI. Does anyone have any suggestions, or at the very least, an explanation why this monitor won't work? Thanks in advance.