The SSR must handle requests to non-existent URLs (e.g. http://localhost:3000/cooperatorxxx) properly and render the 404 page + return a 404 http status code.
This only applies to cases where there is no such route.
If a route exists, but the data cannot be loaded, then that can result in a 200 response from SSR, but it must look like the 404 page. A 404 status code from SSR would be nice, if possible.