Are there any other port configurations on the display so you
may be able to choose an alternative cable to use it? Apple
has a suitable adapter for 30" - & that uses Dual Link (DVI).
• About Apple video adapters and cables - Apple Support
• Displays - Cables, Ports, & Adapters - Apple Support:
https://www.apple.com/support/displays/cables/
Certain display settings may require 'extra effort' or help to make work...
Or a utility such as SwitchResX, a tool for controlling screen resolutions:
http://www.madrau.com/index.html
• How to Show All Possible Screen Resolutions [scaling] for Displays in Mac OS X:
http://osxdaily.com/2015/08/27/show-all-display-resolutions-external-screen-mac/
With the Mini, some displays may use an adapter from Thunderbolt to run
however those options are limited and I've not used them to experiment.
Note ideas in this ASC topic:
Mac Mini 2012 and LG 34" Class UltraWide IPS Gaming Monitor 34UM57-P
Good luck in this matter..! 🙂