Here's a pattern: since your Service Workers won't run the first time a user visits a page, you should send server-side rendered content to the user that also has a line that installs a Service Worker after the page is fully loaded from base HTML with useful data.

The second time the user visits your page, the Service Worker will ideally be installed and will run, intercept the call and download your components separately, when they're needed, and save them on cache, as opposed to let the server render the components to base HTML.

Third time forwards, components are loaded directly from cache and rendered by the Service Workers.

A single page application (SPA) without server side rendering (SSR) doesn't serve "useful data to the user on the first payload". It serves an empty HTML shell with a script tag (or multiple tags) linking to the Javascript app bundle (or multiple bundles). If the app bundling doesn't break up the app into smaller bundles that are asynchronously loaded, the initial JS payload will probably be 10+ MB. At which point the browser needs to download the 10 MB of JS, execute it, and have the JS fill in the HTML with "useful data".

So no, an SPA without SSR doesn't include useful data in the first payload.