Comment by seam_carver

I once had to deal with an old website that ignored the orientation flag in jpg, so my iPhone portrait photos showed up landscape when I uploaded them.

Thankfully Finder in macOS has a way to remove the flag:

How to remove orientation from portrait photo from iPhone on macOS https://youtu.be/lWOlfjVyes4

I couldn’t find a way to do it in Preview, but Finder could do it.