While attempting to connect via SSH tunnel using an identity file and passphrase on the latest stable community version, I was only able to get it to work with an RSA key encrypted with AES-128-CBC or DES-EDE3-CBC. It failed to work with AES-192-CBC, AES-256-CBC, or with an openssh private key.
I got a variety of errors when using these other ciphers, including Uncaught Error: Expected 0x2: got 0x18, Uncaught Error: encoding too long, and Uncaught Error: Cannot parse privateKey: Unsupported key format.
Please add support at least for at least longer key lengths of AES, and potentially for other ciphers and key formats.
Confirmed that I get this same issue on current tip of master for at least AES-256-CBC