As always the Laravel docs are good and key but this file resources/js/bootstrap.js I tend to alter so it looks like this:

window.Echo = new Echo({
    broadcaster: 'pusher',
    key: "your_key",
    cluster: "us3",
    forceTLS: (import.meta.env.VITEPUSHERSCHEME ?? 'https') === 'https',
});

The bottom line seems to help with local development since I do not always have Vite working over HTTPS. Maybe I should fix that 🤔