I was quite disappointed with issue on multiple levels, and I made that known in the threads where I first saw this issue reported - linked below, if you're curious: From the immersive UltraWide display, to the breathtaking clarity of UHD, to the fast and precise UltraGear gaming monitors, LG monitors let you work hard and play hard. And of course the issue with an unknown cause persists. I specifically asked what the underlying cause of this problem was, and he said he'd been told that Dell had decided not to share that information, but that he would be working on getting some sort of official Dell Support article published about this issue.
He did so and then replied back to me saying that he had found internal documentation indicating that all of the following systems had this 1080p limitation on their HDMI outputs:
To download the proper driver you should find the your device. :) Instead of having the power supply inside the monitor, you get a small power brick to. Take it up a notch with the LG UltraFine monitor, boasting an immersive 27-inch display with 5120 x 2880 resolution and 218 ppi that lets you experience the beauty of a MacBook or MacBook Pro on a large 5K screen. I then reached out to an official Dell Support rep who has been helpful getting issues like this escalated internally. Buy LG 34UC79G-B 34 21:9 UltraWide IPS Curved Gaming Monitor 2560 x 1080 Resolution, AMD FreeSync, 144 Hz Refresh. This page contains the list of download links for LG Monitors. It was nice that I did not have to go to a website to find the driver. Browse all of LG’s innovative, state-of-the-art computer monitors, including: 5K monitors. No Sound on my LG Ultrawide and 1080 via DisplayPort. I saw threads reporting this issue involving the Inspiron 34, both with multiple users confirming this behavior.