Bip39 docs https://hubpages.com/@lefwenuuyr Despite the fact that it uses BIP32 technique you could continue to import BIP39 seeds into Electrum wallet. Also besides BIp32 There may be BIP44 Model which some wallet use with the generation of seeds. Exactly how much stability does a passphrase add? A BIP39 passphrase noticeably https://postheaven.net/tiablexcen/recognizing-the-duty-of-bip39-in-copyright-budgets