So I had loads of photos in portrait style by my newer camera that were displayed on their side almost everywhere, except of my usual browser and my home computer. Thanks to Morra for notifying me! There was no other way, only to go ¾ of the year back and to rotate them. It seems the problem is the „orientation“ in EXIF. No idea why, but the steps „rotate counterclockwise“ + „rotate clockwise“ in the File Explorer produce the photos that are displayed correctly in the other browser as well (have no idea about other devices while at home).
And this is why the old camera is still very handy sometimes. It doesn‘t get its own ideas about gravity.
And this is why the old camera is still very handy sometimes. It doesn‘t get its own ideas about gravity.