(sorry for my bad english)
when display qhd image to qhd monitor with letter size slide, it show compress artifact like low resolution image but it is same size image captured from same monitor.
and the same file displayed normally at MS powerpoint, but libre impress show artifact like low resolution image.(some characters are broken)
[QHD capture] → [full letter size slide(maybe resize temporarily)] → [slide show in QHD monitor]
We internally have a limit for an image size in our filters; and the image might actually be downsampled when processed. But it might need to be changed, given the hi-resolution images become more widespread and useful (like in your case); possibly the limit should be dynamic, dependent on the actual monitor used.
It’s best to report it as a bug, attaching a sample ODP with such image, and also screenshots of the result and of expected result (e.g., from PowerPoint).