Thanks for posting here! The tech specs of DELL E248WFP states that the native resolution is 1920 x 1200. Hence the aspect ratio is 16:10
The maximum resolution that the DisplayLink DL-165 chipset inside the graphics port on the Plugable UD-160-A supports is 1920 x 1080 which is lower than the native resolution of the monitor. The aspect ratio of this resolution is 16:9.
When you set the resolution to 1920 x 1080 for this monitor on the system, the monitor is not able to display as the aspect ratio is different.
At 1680 x 1050 resolution, the aspect ratio is at 16:10. This aspect is supported by monitor and hence it can display at this resolution.
Although the graphics port on the Plugable UD-160-A supports the resolution 1920 x 1080, because of the mismatch in aspect ratio, the monitor is not able to display at this resolution.
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