OpenConnect can be installed via homebrew:

      brew update
      brew install openconnect

Running openconnect requires sudo, presumably because it affects resolution of DNS, but you can add password-less sudo ability for the openconnect command.

Open:

      sudo visudo -f /etc/sudoers


Add this line:

      %admin  ALL=(ALL) NOPASSWD: /usr/local/bin/openconnect

Entering password each time, when you connect to VPN, can be annoying, so you can store it in the keychain.

Open "Keychain Access" app, click "File -> New password item". Once it's created, you can access it from the command line using`security find-generic-password -s <keychain_item_name> -w`.

      security find-generic-password -s vpn -w | sudo openconnect --user <username> <host>