A quick answer from the road on this one. This is explained in the docs:
Whenever an option is selected,
LiveSelectwill trigger a standardphx-changeevent in the form. See the “Examples” section below for details on how to handle the event.
A live select input behaves like an ordinary select input, the change event is triggered when the user selects one of the options. No need to implement new messages. Let me know if this isn’t explained clearly enough in the docs or if you’re still struggling.
