OpenSSH SSH-2 private key (old PEM format)
Taken from here: https://stackoverflow.com/questions/60884217/openssh-ssh-2-private-key-old-pem-format-on-azure-linux-vm You’ve used ssh-keygen to create a private key file called id_rsa.ppk. However this is an OpenSSH-format private key and needs to be converted to Putty’s own format to use in Putty. Your options are: