There's only 1 way to do things in the NIPs. But the clients are a free-for-all. How do you log into Nostr? If you have to say "it depends", there's a problem.

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.

Each brand will solve this UX in their own way, though we'll see some patterns emerge It's not a problem, it's to be expected if this is a decentralized network