I recently bought a MacBook Pro 13-inch 2017 and an LG Ultra HD (27UD88) 27" display. Before buying the display I researched a bit and found no issues in relation to the MacBook Pro.
However, after attaching the screen via the USB-C cable that came along with the display, I only have the option of a 30hz refresh rate.
I've Googled this without finding much - it seems like no one else is having this problem. From a result, I've also learned that my "Display" page in "System Preferences" looks slightly different than a screenshot from an article.
- http://www.lg.com/us/monitors/lg-27UD88-W-4k-uhd-led-monitor (LG official page, shows 60hz)
- https://9to5mac.com/2016/06/04/how-to-enable-4k-60hz-resolution-2016-macbook/ (speaks of a patch needed for MacBook 2016)
- https://www.reddit.com/r/apple/comments/5azoij/2016_macbook_pros_and_lg_27ud88/ (at least one use confirms 60hz with MacBook Pro)