The full site mode & posting pictures via my iPhone 6P has become a real PITA lately. I honestly wait until I get home now and do it from a PC.

 

 

Upload the picture at any picture site, I prefer to use imgur (quick, easy to use) and then use the function called "Image" and put the link to the file (not to the preview page), example: link preview - https://imgur.com/a/HqLWqSa, while the same link to file - https://i.imgur.com/bbzEdB0.png - as you may note, it's quite different links. Hope this helps!