Doesn't help in this case but in your /etc/ssh/sshd_config or similar change or, if missing, add PubkeyAuthentication yes ChallengeResponseAuthenticat

Doesn't help in this case but in your /etc/ssh/sshd_config or similar change or, if missing, add PubkeyAuthentication yes ChallengeResponseAuthentication no PasswordAuthentication no PermitRootLogin no Make sure you can log in using your key and su/sudo from that unprivileged user before applying those changes.