The Dropsource docs suggest to check Apple official launch screen settings, but on that page, it suggests NOT to use a static image, and to use XCODE instead.
“It’s best to use an Xcode storyboard for your launch screen. If you must provide a set of static images, create them in different sizes for different devices, and be sure to include the status bar region.”
Is there a way to use a dynamic image?
Failing that, is there a way to import different size static images as they suggest?