Unfortunately my understanding is that this is essentially impossible. SMB hashes the password on the client-side, and the hashing algorithm isn't compatible with the algorithms used in /etc/shadow (it's unsalted and less secure). I doubt Linux distros would want to have another field in /etc/shadow just for Samba passwords, and deal with keeping them in sync.
Samba can use standard Linux users, but there's no way to reuse the same passwords.
If it really bothers you, I think you could set up authentik (or some other idp) and point all your login needs at it... Though, it's not going to make things easier for you, just the opposite. Probably a good learning experience though.