A chave privada era inválida. Um único caractere estava faltando. A saída é alterada da seguinte maneira quando uma chave privada válida é usada:
debug1: Offering RSA public key: root@etoorlan4c
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: sshkey.private
debug3: sign_and_send_pubkey: RSA SHA256:jmMyCOppv3KKkRgiHI4s5h3I7LwyCgms8uSG06KClQ4
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (publickey).
Authenticated to [remoteHost]([xxx.xxx.xxx.xxx]:22).