Following up on this. You have hit an issue where OpenSSH have broken support for clients that advertise support for SSH version 1 and 2 (ssh 1.99). This occurs with OpenSSH 7.6 which is bundled with Ubuntu 18.04.   This is fixed in OpenSSH 7.7+ http...

@sukala Since you don't have any ROMMON variables configured, You need to select option 1 first (32 bit Classic), break & enter ROMMON, configure ROMMON IP/Mask etc, then reboot to the 64-bit boot menu again & then select Option 4. From there you can...