Not sure if there is interest in merging a PR for this, so I decided to open an issue first.

Apparently, the splash image for iOS needs to be sized exactly to the screen to be displayed. The official documentation doesn't mention this, but there are lots of articles/blog posts (like this one and this one) that do cover this constraint.

This leads to a horrible mess of link tags to match every possible Apple device and entire projects dedicated to generating these images.

Instead of managing this here, I suggest adding a filter (maybe apple_touch_startup_image) that plugins/themes can use to add all the splash screens they want.