Mac Mini 2018 and LG 49WL95C-W 49-Inch Curved 32: 9 Ultrawide

I just purchased a Mac Mini (although in the system preferences it says that is a 2018 model); however, it is the latest model. I also purchased an LG 49WL95C-W 49-Inch Curved 32: 9 Ultrawide monitor. The monitor runs perfectly fine with my laptop (MacBook Pro 2017 model) at the expected resolution (5120 x 1440).

However, the Mac Mini can only go to 3840x1080.

After reading about external GPUs, I decided to buy a Razer Core X Aluminum External GPU Enclosure (eGPU) and a Radeon Rx 590 Gaming 8G Graphics Card,(Gv-RX590GAMING-8GD). After spending more than $3500 in this setup (without monitor), the Mac Mini still does not work at 5120 x 1440. However, my older Mac Book Pro does.

Any other suggestions before I return all of these?

Thank you in advance!