It's not easy to use a launch screen storyboard that uses different images for iPad in portrait and landscape mode. For the iPhone this can be solved using height and width classes. But as iPads have regular height and regular width it's not possible to determine the orientation of the device within the launch screen storyboard.
This iOS project has an adaptive launch screen storyboard using spacer views that position the correct image in the visible area and move the other one off screen.
You can NOT provide different images for different screen sizes (iPhone 4, iPhone X, ...), but if you want different images for iPhone and iPad and different images for portrait and landscape this solution is for you.
The important constraints are
PortraitSpacer.width ≤ 5 × view.width
PortraitSpacer.width ≤ 5 × view.height
LandscapeSpacer.width ≥ 5 × view.width
LandscapeSpacer.width ≥ 5 × view.height
PositionSpacer.width = 5 × view.width
where view.width and view.height are the main view's width and height.
The PortraitSpacer positions the portrait image at 5 × min(view.width, view.height),
the LandscapeSpacer positions the landscape image at 5 × max(view.width, view.height),
and the PositionSpacer has the same width as PortraitSpacer in portrait mode and the same width as LandscapeSpacer in landscape mode.
We multiply everything with 5 so the two images do not overlap. This works for all devices where the following is true
5 × min(view.width, view.height) + max(view.width, view.height) ≤ 5 × max(view.width, view.height)
In landscape mode this would mean
5 / 4 ≤ view.width / view.height
which is the case for all current devices: iPad has the lowest aspect ratio with 4:3 which is still greater than 5:4.
You can then of course configure images per device (iPhone, iPad) in the asset catalog.