I Know that the keychain will be maintained even after an app is uninstalled.
However, is there a way to remove the keychain for users? Like, restore the whole phone.
Thank you in advance!
You have no callback or method of removing the keychain items on deletion of your app, so there's no individual way to remove a single keychain item.
If you restored the entire phone to factory defaults Settings -> General -> Reset -> Erase All Contents and Settings, then it would be removed (along with everything on the phone!)