The hardware wallets, e.g., Trezor and Ledger, support bip39 with an optional passphrase. In theory, since bip39 is a standard, you should be able to recover these hardware wallets to any ethereum wallet, but I am having difficulty finding software wallets that support the optional passphrase.
Which wallet generators allow you to specify an optional passphrase when generating the mnemonic seed?
Which wallet programs allow you to import bip39 mnemonic seeds with a passphrase?
If I already have an address I'm happy with, is there a tool that can show me what the corresponding mnemonic seed would be that, when combined with a given passphrase, would yield my current address?