LG 38UC99-W can't display its full native default resolution on Macbook Pro

[dneyhigg]

I just got a new LG 38UC99-W ultra wide display, primarily to be able to edit video in Premiere Pro on my work-issued MBP, with ample screen real estate.

These are the specs of my work-issued MBP:

MacBook Pro: MacBookPro10,1 (Retina, Mid 2012)
Processor: 2.7 GHz Intel Core i7
Memory: 16 GB 1600 MHz DDR3
Graphics: NVIDIA GeForce GT 650M 1 GB / Intel HD Graphics 4000 1536 MB
Mac OS: Mojave 10.14.6

I have the LG monitor connected here via HDMI cable that came with the display, and all is GREAT, working in 3840x1600 as expected:

I also have my personal MBP, which is more recent & with upgraded graphics card, & running MacOS Catalina:

MacBook Pro: MacBookPro11,5 (Retina, 15-inch, Mid 2015)
Processor: 2.8 GHz Quad-Core Intel Core i7
Memory: 16 GB 1600 MHz DDR3
Graphics: AMD Radeon R9 M370X 2 GB/Intel Iris Pro 1536 MB
Mac OS: Catalina 10.15.5 (19F101)

But when I attach the LG display to it using the same HDMI cable, the display is unable to set to the default 3840x1600 as "default for display"

Is this possibly a Catalina issue? That and the different graphics cards are the only variablI can't imagine that my AMD Radeon R9 M370X 2 GB wouldn't also be able to drive this display to its native resolution.

Anyone else run into this or a similar situation and can point me in the right direction?

 

[robvas]

It’s doing HiDPI, you could probably fix it with SwitchResX

Also, you are running 30hz, I would connect over DisplayPort so you can run 60hz