Install the plugin jar file in your hub server(s):
1.13.2+         ServerSelectorX-Premium-2.1.5.jar           Requires Java 11+
1.7.10-1.12.2   ServerSelectorX-Premium-2.1.5-legacy.jar    Requires Java 8+

Wiki: https://github.com/ServerSelectorX/ServerSelectorX/wiki

SSX-Connector is for sending data about a server to the hub server, so it is possible to display detailed server information in the menu. Install it on all servers: https://github.com/ServerSelectorX/ServerSelectorX/wiki/Installing-SSX-Connector

The one SSX Connector jar file works with all versions from 1.7.10