Just a reminder for everyone that by default SSH leaks all of the below public keys (if they exist) + all public keys in your ssh-agent to every server you connect to.

    ~/.ssh/id_ecdsa.pub
    ~/.ssh/id_ecdsa_sk.pub
    ~/.ssh/id_ed25519.pub
    ~/.ssh/id_ed25519_sk.pub
    ~/.ssh/id_xmss.pub
    ~/.ssh/id_dsa.pub

Your "leaked" public keys can be used to check if a certain server recognizes that key.