4k60hz is also possible over displayport, on my Late 2013 mbp I need to use switchresx to get it going (but I've found that pretty set-and-forget), but on the newer ones than that it works without any hacks AFAIK
If it's HDMI only, as the sibling pointed out the HDMI port won't work. However, Startech makes a displayport to HDMI adapter which works ( https://www.amazon.com/DisplayPort-HDMI-Adapter-Converter-60... ) (just make sure you get one which supports 4k60hz, most DP -> HDMI adapters don't).