This article explains how to change the Safari iOS search engine from the default Google to another option, such as Bing, Yahoo, or DuckDuckGo. Information applies to Safari on iOS devices running iOS 14 through iOS 10.
How to Change Safari's Default Search Engine on iPhone and iPad
To change the default search engine that Safari uses on iOS devices:
Open the Settings app from the home screen of your iOS device.
Scroll down and tap on Safari.