Question: Why do my photos look flat and dull once I upload them from Lightroom to Instagram?
A
Answer: The export is almost certainly carrying the wrong color space, and Instagram finishes the job. Export sRGB JPEG at 1,080 pixels wide and the flat look goes away. If the colors are right but the file looks soft, Instagram scaled your file down, because it keeps feed photos at a maximum width of 1,080 pixels. If skies turn into flat bands of tone, the file only has 8 bits per channel, so export from 16-bit and convert before you upload.