Black background for app icons on my iPhone with iOS 18.2 post rebooting

I rebooted my iPhone (iOS 18.2), and now the screen with all the app icons and icon folders has a black background. How do I switch this back to a light background? When I switch from the lock screen to that screen, it momentarily displays things properly, and then the background suddenly switches to black.

[Re-Titled By Moderator]