Thanks @nerlichman!

Do you think we should go further, drop ssr/ssr.tsx, and pass entry point to inertia vite plugin instead?

inertia({
  ssr: "app/frontend/entrypoints/inertia.tsx",
}),

Yeah, sounds great!

I'll also need to guard initializeTheme() on the entrypoint:

if (typeof localStorage !== "undefined") {
  initializeTheme()
}

I enabled SSR to test and found a few errors.

First in the vite config, setting this results in SSR ERROR ... module is not defined:

  ssr: {
    // prebuilds ssr.js so we can drop node_modules from the resulting container
    noExternal: true,
  },

In order not to remove this, the solution I found was doing the following:

export default defineConfig(({ command }) => ({
  ssr: command === "build"
    ? { noExternal: true } // prebuild ssr.js so we can drop node_modules from the container
    : undefined,
  plugins: [
//  ...

But I'm not sure if this is correct.

Another thing is that I also realized that SSR is not working, due to hooks/use-mobile.ts using window. But I thing this is better to address on a separate PR.
EDIT: I updated the hook with a guard to check if window is defined.

What do you think?