Cannot authenticate by NX protocol with a private key generated with openSSH 7.8p1-1 or later
SSH key pair generated by openSSH version 7.8p1-1 or later cannot be used for key-based authentication by NX protocol. The same key-pair can be used instead for NoMachine connections by SSH protocol and key-based authentication.
As a workaround, convert the existing SSH private key by using this command:
ssh-keygen -p -m PEM -f path_to_the_key
SOLVED, Released in version 6.9.2
