I have a use case where I need to "generate" mobile apps with a specific package name (Android) or Bundle Identifier (iOS).
As this should be able to run on all operating systems (macOS, Windows, Linux), just using e.g. the Xcode command line tools is not an option. So I though about using fastlane.
I created template projects with Android Studio and Xcode once, then checked the results in to version control as a "template".
How can I rename those iOS and Android projects using fastlane?
Android
I have an Android plugin that renames package names and moves around the directory structure to "work" (but this might not be the best/cleanest solution) - https://github.com/joshdholtz/fastlane-plugin-rename_android_package
iOS
For iOS, you can simply change the bundle identifier in the Info.plist file. This is all that is really needed to make the app new/unique. You can use the update_app_identifier action that fastlane provides.
Then you will have to create this new app in the iOS Developer Portal and create new provisioning profiles (all of which can be done with fastlane actions produce and match/sigh).