Yes, close to 100% paste in I'd imagine. There are workarounds such as nsec.app, Aegis, Nosskey (piggybacking off passkeys), and some extensions, or apps like Damus/Nostr attempting to be your signer, but any solution that keeps it all local faces the same fundamental issues and can only half-overcome them. There can never be an Amber on iOS.

Cloud enclave based can potentially scale but needs a lot of work, Artur is the brains there, we're working on it too, but needs time.