As far as I can tell, the issue of thumbnail images being rotated has not been "fixed" yet. I realize that some phpbb members/developers do not see this as a phpbb issue that needs fixin', but again I add my name to the chorus of phpbb board admins that don't care which piece (phpbb code, plupload code, ImageMagic code, extension code) is broken or who's fault it is - we just want a solution.
Telling 2000 forum members never to rotate their smart phones and tablets (and in some cases, digital cameras) is not the solution.
In most cases, a "forum" is no longer a "bulletin board" full of text. Modern forums are image-heavy, and server space is cheaper, so more forums are now allowing attached images. The cameras/phones/tablets produce huge files, needed for printing, but we sure don't want those giant files in our servers for monitor display (so the plupload "quality" attribute is critical.) Improperly rotated thumbnails from attachments are making phpbb look bad. None of the members know about the 3rd party libraries and code that is used along with phpbb - they simply see it as phpbb developers unable to solve the issue. It will appear as phpbb's flaw until solved.
There are some very good software developers here, both within the phpbb core team, and other developers adding extensions. I'm an old dinosaur programmer and a newbie at php, or I would dive in to the code. I'll bet someone here could fix the issue in an hour of programming. Maybe 3Di already is
, but once the issue is resolved, it really should be in the phpbb core code, not in an extension.