To remove a wallpaper on your iPhone, open Settings, tap Wallpaper, then Add New Wallpaper, and choose a new color or photo.
On any modern iPhone the core path is the same.
Your iPhone keeps two separate backgrounds.
This is the genuine removal method most people are hunting for, and it only exists on newer software:
Live wallpapers animate when you press the lock screen; Dynamic ones drift subtly on their own.
Read the complete breakdown, fixes and what happens next.