iPhone 8 Plus requires iOS 17.0 update

Your iPhone 8 Plus is correct. The application that you are trying to run requires iOS 17 (or iOS 18).

What your iPhone 8 Plus is not telling you is that it is not capable of installing iOS 17 (or iOS 18).

If you really do need iOS 17 or 18, you need a new phone......an iPhone XR or higher model. My advice would be to buy the newest model of iPhone that your budget allows.

If you need the application, then you'll need to buy a new or newer model iPhone as iPhone 8 cannot run iOS 17 or higher at all. iOS 16.7.10 is currently the highest version an iPhone 8 can run.

What you’re experiencing is typical.

Lack of “older” OS support by 3rd party “critical applications” is what often forces one to upgrade their still-functioning devices.

Banking apps are often some of the first to go.