How do I update my iPhone 8 Plus to latest iOS version?

An iPhone 8, iPhone 8 Plus, or iPhone X isn't capable of 17 or above; they require an A12 or better CPU. To install 16.7.10, use a computer or the Software Update function in Settings.

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You cannot update an iPhone 8 Plus to the latest iOS version.

For the iPhone 8 Plus, iOS 16 is the end of the line.

About iOS 16 Updates - Apple Support

Update your iPhone or iPad - Apple Support

Updating iOS: common issues and solutions - Apple Community

The latest iOS version for your iPhone 8 Plus would be iOS 16.7.10.

Unless you have not updated your iPhone in a long time, you already have iOS 16.7.10 installed.

The iPhone 8 Plus cannot run iOS 17....(now discontinued)....or iOS 18, if that might be what you were asking about.