LG 4k display (27UK600) not recognized at proper resolutions after upgrade to Mac OS 10.14.6

I have been using my 2017 MacBook Pro with an external LG 27UK600 3840x2160 4K Display. It is connected via HDMI and a USB-C hub. For years, through Sierra, High Sierra and Mojave it worked fine. Then, after upgrading to 10.14.6 three days ago, I got home and plugged in my display and now it is only recognized as supporting resolutions up to 1920x1080:

I have restarted everything multiple times. I have plugged and unplugged. I have swapped out the USB-C hub for a different one. I have reset the SMC and the NVRAM. I have spent hours on the phone with 2 different senior advisors at Apple. Most recently, the apple advisor told me I needed to upgrade the firmware on my LG display and that I should call LG so then I spent a half hour with them on the phone so they could confirm that they don't actually publish firmware updates for their plug-and-play displays.

Any ideas?