iOS will not offer saved credentials for associated domains

When filling in a username and password on iOS, if you have setup an associated domain with 'webcredentials', iOS should display your saved credentials as an autofill option. This does not happen regardless of whether you use plain HTML, Angular forms or Ionic input elements.

iOS will display the 'passwords' button allowing you to search keychain for the relevant saved credentials however it will never offer the previously saved credentials.

https://forum.ionicframework.com/t/how-to-autofill-password-on-ios/199744