This post will try to help you get a openvpn connection on a chromebook with a pushed route instead of a redirected gateway. By default chromeos redirects all traffic to the vpn. To overcome this you can make a onc file that can use all the ovpn config options instead of the very limited gui options.
To start you will need the following files:
ca.crt client.key client.crt client.ovpn (or equivalent) # user and pass auth enabled in server (auth-user-pass) At the end you will have 3 files that will allow you to connect to the vpn.