This works without the SSH SFTP Updater Support Plugin on PHP7:
Create an ssh keypair (ssh-keygen -t rsa -b 4096).
define("FS_METHOD", "direct");
define('FTP_CONTENT_DIR', '/wp-content/');
define('FTP_PLUGIN_DIR', '/wp-content/plugins/');
define('FS_METHOD','ssh2');
define('FTP_PUBKEY','/home/USER/.ssh/id_rsa.pub');
define('FTP_PRIKEY','/home/USER/.ssh/id_rsa');
define('FTP_USER','USERNAME');
define('FTP_PASS','');
define('FTP_HOST','HOSTNAME.evermore.com:PORT');
# Added by ACC 5/9/2014
define( 'FS_METHOD','ssh2');
define('FTP_USER','[username]');
define('FTP_PASS','[password]');
define('FTP_HOST','HOSTNAME.evermore.com:PORT');
This seems to work erratically. Hypothesis: you have to add the lines to the bottom of wp-config.php, install the plugin from the CLI, activate it in the WP web GUI (or activate, deactivate, activate), THEN try to have it install something.