If you search GitHub for prod.keys , you will see results. These are publicly shared decryption keys. While you may be tempted, using keys dumped by a stranger ties your usage to a stolen console certificate. Nintendo has bricked online functionality for users using mismatched key sets.
While the original Yuzu repository is gone, the community maintains several "mirror" or "archive" repositories. You can find firmware by searching GitHub for these specific terms: yuzu emulator firmware download github
This guide explains how to properly handle firmware and keys to keep your setup functional and secure. If you search GitHub for prod