I just started a new remote job. They shipped me a 2018 15" Macbook Pro, a 32" Asus PB328Q monitor (QHD, aka 2560x1440), and a Satechi USB-C adapter, with an HDMI cable for connecting the monitor. All of the above were used previously by a former employee. I am running macOS Mojave 10.14.6; upgrading to Catalina is not an option at the moment for IT policy reasons.
About 90% of the time (including right now), when I connect the monitor, the system runs it at 1080p resolution. As expected when running at non-native resolution, everything is blurry onscreen and I don't get the real estate I want.
If I unplug and replug the adapter from the laptop, or the HDMI cable from the adapter, there's a small chance it will come back at the right resolution. I have only had this work when plugging into the left-side ports on the laptop.
The Displays prefpane's extra window for the monitor shows that it is being recognized correctly as a PB328. Option-clicking on Scaled to reveal more resolutions does not help. (By default, only four resolutions are shown; option-clicking reveals several more, but none larger than 1080p.)
If I unplug and replug repeatedly, eventually the native resolution shows up. At the same time, the Refresh Rate dropdown is disabled and the Underscan option disappears. Perhaps these are useful indicators?
I found this related question, which has no accepted answer. ColorSync Utility reports "No problems found." The monitor does not support HDMI 2.0, so that can't be the problem. I am on the latest version of Mojave and this monitor is not new, so I don't think graphics drivers could be it.
Could this be related to switching between integrated and discrete graphics? If yes, how can I confirm and/or control that?