I don't understand this condition: > if using a single backup and index based derived key sets including BIP85 32bit hex keys used as nsec. But if I could get away with ignoring it, I would only quote this part: "I think it is the only option" and then I would say "it's clearly not the only option because bitcoin core doesn't use bip39." Sadly, I can't say that without doing an injustice to what you said