Answered elsewhere in this thread by EliteMasterEric:

Someone else mentioned that when an image gets uploaded, any metadata gets stripped. The metadata can include GPS coordinates or other information about the camera that took the photo, so it’s important to strip it, but it also includes a flag for what orientation your phone was in when you took the picture, the idea being to differentiate between landscape and portrait pictures.

Not sure what the best way for lemmy to fix that is.