Do you know if there is a way to use a passphrase with this HD seed like we can do with BIP39 memonic seeds? With a Bitcoin Core feature or an external tool.
So far, there's no BIP to encrypt HD/BIP 32 seed with password/passphrase. The other option is use common encryption algorithm (such as AES-256) through offline/open-source tool such as
https://cryptotools.net/aes. But since it's not standard/popular method to encrypt HD/BIP 32 seed, you also need to write down how to encrypt/decrypt it and backup relevant software/tool.
That's what scares me, having a hidden bug when using the tool to encrypt the seed or not being able to find a good version of the tool when I want to decrypt the seed in several years. That's why I'd need a very standardized and and safe tool to encrypt. BIP38 seemed perfect for that.