Monitor Resolution Problems in Mohave

I found out what the problem was. Even though my LG 32UD59 monitor was bought only 3 years ago, Mojave didn't have a driver for it. I bought a new 2k monitor, Mojave recognizes it and it works fine. I think there could be better updates from LG to Apple - that monitor is too new to be obsolete in Mojave.

Thanks for your reply. Actually for me it's the option key which shows more resolution choices, and the 2440 resolution can only be seen this way. It also has (low resolution) shown after the numbers, as do all the resolutions seen when using the option key. My monitor is also connected by HDMI, but there are no settings having to do with resolution, only different color options, and definition settings. In Mavericks, all the definitions look fine, just personal taste. In Mohave, there is no definition setting that looks good - it's a mess. All I can think of, is that somewhere between Mavericks and Mohave, Apple changed a driver which makes this monitor incompatible with a 2440 resolution, and changing to that resolution causes the monitor to show warning badges. Maybe I'll have to find a different monitor which is OK with 2440 if I want to upgrade to Mojave.

Thanks for your reply. I called LG today and was told that they don't make drivers for Mac - the drivers for LG monitors are included in the Mac OS. In System Preferences/ Displays, all the resolutions are different in Mavericks than they are in Mojave. The only resolution common to both is 1920 x 1080. That's what makes me think that Apple must have changed the driver sometime after Mavericks.