ref: https://developer.apple.com/design/human-interface-guidelines/ios/app-architecture/launching
Launching screen
Displaying the launch storyboard assures the user that your app launched and is doing something.
The launch screen isn’t an opportunity for artistic expression.
Also make sure that your launch screen matches the device's current appearance mode; for guidance, see Dark Mode.
Launching screen 에서도 darkmode 사용해라.
Dark mode
Comply with the appearance mode people choose in Settings. If you offer an app-specific appearance mode option, you create more work for people because they have to adjust more than one setting. Worse, they may think your app is broken because it doesn't respond to their systemwide appearance choice.
Ensure that your content remains comfortably legible in Dark Mode when you adjust the contrast and transparency accessibility settings
Prefer the system background colors.
Orientation
Launch in the appropriate orientation. If your app supports both portrait and landscape modes, it should launch using the device’s current orientation.
don't ask for setup setting
Avoid asking for setup information up front. People expect apps to just work. Design your app for the majority of users and let the few that want a different configuration adjust settings to meet their needs. As much as possible, get setup information from device settings and defaults, or through a synchronization service, such as iCloud. If you must ask for setup information, prompt people to supply it the first time they open the app, and let them modify it later in your app’s settings.
