These days photos have an 'orientation' tag set in the EXIF information embedded in them. So instead of rotating the entire image, it just tells the software to show it in a particular direction. As mentioned above, this tag is sometimes set incorrectly when a phone is used to take a picture in a near horizontal orientation. That would show up on the phone as well though. It is more likely that the software being used (Openboard) is not able to deal with these orientation tags. You're on the right track in using a photo editor to fix this, but I would suggest that after you open it in a photo editor and making any adjustments necessary, you save a copy of the photo and use that. I have not tried it, but that may 'reset' the orientation tag to the correct attitude.