If you use an iOS or iPadOS device, you don’t need an antivirus app. Period. Because of the way that Apple’s mobile operating system is set up and maintained, viruses can’t affect most parts of your system. While iOS vulnerabilities and malware can exist, there’s little that an antivirus app can do about them.
Because of that, many antivirus apps for iOS are disreputable or nonfunctional. And some of them may try to scam you out of money via in-app purchases or subscriptions. If you’re concerned about viruses on your iPhone, don’t be. A little vigilance will do a lot more for your security than any antivirus app on the App Store.