Somebody correct me if I’m wrong, but I don’t think Yuzu has any proprietary code. Folks have to go to other websites to download the Switch firmware and keys needed to play games.
Maybe I’m misunderstanding you, but backend servers will almost always have the user-submitted password in plaintext as a variable, accessible to the backend server and any upstream proxies.
It’s even how it’s done in Lemmy. The bcrypt verify accepts the plaintext password and the expected salted hash.