Low quality export file
When exporting to JPEG, I have noticed that I get a significant drop in image quality when exporting to the max size (leaving 0x0). The result is much better when I use 1080x1920 (for example) as the max size. As you can see in the image, there is much more stars in the lower quality image. The result with the lower size image is much more closer to what I can see in the DT viewer.
I have taken my photos with a OnePlus 3T and edited the dng files on Darktable 2.4.4 on Windows 10.