My Lightroom mad. He does not want for anything to export image format 1030x578 . Why ?, if so I want to ...
The image has to be cropped to the correct aspect ratio before you export it. 1030 x 578 equals 1:1.782.
Most digital cameras have an aspect ratio of 2:3 or 3:4.
So you need to crop the image in Develop to an aspect ratio of 1030 x 578 before you export it.
In the Crop panel, click on Original next to the padlock, and choose Enter Custom. Then enter 1030 x 578.
Note that the crop tool only crops to certain proportions, not to pixel dimensions.
Pixel dimensions are set in the Export dialog. (you would only need to set Long edge to 1030 pixels)