I will not advice you to use many of the BIP39 wallets because they are close source,
Bip39 wallets are
not closed source. This is inaccurate. "BIP" stand for Bitcoin Improvement Project" and all BIPs are very much open source.
A "Bip39 wallet" is nothing more than wallet backed up by a seed phrase that was generated from a specific (open source) word list. That's all. Many wallet
clients will allow you to import a Bip39 wallet. Many of those wallet clients are also open source.