We can't control window's location on Wayland, so there is no way to place splash screen at screen center.

Discussion:

This is due to Wayland not allowing windows to position themselves.

This will need a Wayland protocol extension to add a role(https://wayland-book.com/surfaces/roles.html) for an output-only, centered surface.

it'd just need a fallback implementation for compositors that doesn't support it, e.g. a dialog

Add input to this existing issue : https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/67

Implementation will probably be similar to this MR for Picture-In-Picture video: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/132