How do you make it so players can teleport doing /servername

You can setup aliases whenever they do /server Hub, to something like /hub or /lobby. If you're looking for a plugin that can do this, you can use MyCommand.

https://www.spigotmc.org/resources/mycommand.22272/



Other Ways:
https://www.spigotmc.org/resources/multilobby.2446/
https://www.spigotmc.org/resources/redirect-plus.51975/