To me the onboarding MUST be done by a Nostr-only App Store. I don't want to onboard to an app. I want to onboard to an ecosystem of apps and allow the user to choose. User creation can be done by the store. Imagine if @Zapstore had an onboarding screen that automatically installed Amber and logged into that for the user. Now you have a signer for all the other apps you may want to install. The goal is to onboard to Nostr, not to any specific brand inside of Nostr.