This happens because the forum software is unable to read the EXIF data that is imprinted on the photo when you take it.
The EXIF data holds a lot of information, which includes orientation of your photo. Many programs are able to read this, and that is why you see it displayed upright in some places, but many others still are not.
This is a good article that explains all of this: https://www.howtogeek.com/254830/why-your-photos-dont-always-appear-correctly-rotated/
The gist of it is, the phones are designed to work like a digital camera. Holding your digital camera flat, in landscape, is the 'base line'. Developers used this 'base line' in the following way for mobile devices:
Apple users: hold your phone with your VOLUME buttons DOWN.
Android users: hold your phone with your HOME button to the RIGHT.
It's completely against common sense since the volume button is used as a shutter button, so you would think the volume button should point UP! But that is how developers worked it out, so when you hold your phone upright, in portrait, it is the same as turning your digital camera 90 degrees to the side, to take a portrait photo. Since the forum cannot read the data that tells it which way you are holding your phone, it displays plainly from the 'base line' - whichever side your volume buttons are on will be the bottom of your photo (so if you take a photo with your volume buttons facing UP on your phone, the photo will display upside down when you upload it here).
There is not currently any plugins or hacks that we've come across that can allow the forum to read the EXIF data at this time.
The only way around it is, either hold your phones the way the developers decided you should, OR you can open the photos in an Editing program (not the viewer), and save them in the correct orientation (you might need to rename them, and crop off a pixel or two, to make sure a change is recognized).
Hope that helps!
Thanks Gerritt, thats great info. It seems pretty easy to edit a photo’s orientation in the apple photos app. I’ll give it a try next time. I’ll also remember to hold my phone with the vol buttons toward the bottom in the future. Thanks again.