Forgive me if this is the wrong way to report a bug to Adobe. It was all I could find.
This bug occurs only with the latest version of LR Mobile for iOS - ver 3.0.0 when running on an iPad. It does not occur when using the new version of LR Mobile for iOS on an iPhone (at least not on an iPhone 7). The previous version 2.6.1, behaves properly on both tablets and phones. I am running the new LR Classic, ver 7.0 on my Mac and I have installed LR Mobile for iOS 3.0.0 on a 9.7 inch iPad Pro, updated to the latest version of iOS, ver 11.0.3.
The problem involves selecting an image from a synced collection where the image is in landscape orientation and the tablet is being held in portrait orientation. When the image is selected, it first behaves properly, expanding as much as it can to fill the space between the edit menus and the left side of the display while still showing the entire image. BUT if you turn the tablet to landscape orientation to match the orientation of the image, the image DOESN'T CHANGE SIZE. Instead the pixel dimensions of the image remain the same so you have an image that uses only the center part of the display. But we aren't done with the weirdness yet. If you now rotate the tablet back to landscape orientation, the image DOES change size. It changes to the size that it should have been when the orientations matched. But since the tablet is now being held in portrait orientation, you can only see part of the image. The image aligns with the left side of the display and shows as much as it can in the space between the left side and the menu bar. If you now rotate the tablet back to landscape orientation again, the image size again remains the same, but this time that is what you want, you just had to go through two additional rotations of the tablet to get there.
But here's the thing, if you follow the procedure above, but before doing any rotating of the tablet you tap the image once to hide all the interface elements (toolbar, film strip, etc), then everything works properly when you rotate the tablet. However, if you tap again to turn all the interface elements back on, the weirdness described above returns.
NOTE: Portrait oriented images display properly, regardless of tablet orientation. This only happens to landscape oriented images.
There is one other kludge you can use to get around this without turning off the interface elements. After rotating the tablet from portrait mode to landscape mode and finding the image is smaller than it should be, you can double tap the image to expand it to 100% and then double tap again to get it to fit properly within the tablets landscape orientation. But, if you rotate the tablet back to portrait mode, the image WILL NOT scale back down. You will have to double tap it again to see the entire image.
And finally, all of this craziness continues if you select a tool from the menu bar. It just happens within a smaller screen area.
I sure wish I had ver 2.6.1 back on my Baby Pro tablet. At least 2.6.1 is still on my 12.9 inch iPad. Hopefully this bug will be corrected quickly in a 3.0.1 update. Depending on what the community has to say, I would hold off on updating LR Mobile for iOS to ver 3.0.0 for now.