I'm using a LuisDialog and all I get the the callback returns is an IDialogContext and the LuisResult.
Is there a way I can get info from the original Activity, like channel, from name, et al?
In the latest release you can access the original incoming message from the intent handlers. Check here to understand how your intent handler should looks like.
public async Task MyHandler(IDialogContext context, IAwaitable<IMessageActivity> activity, LuisResult result)
Alternatively, you can use context.MakeMessage but I would recommend updating your intent handlers.