The "Dynamic `href` is not supported in the App Router" error happens when you try to use a dynamic `href` with `next/link` in the `app` directory.
The new client-side router in Next.js does not use a mapping of dynamic routes to URLs, but rather it leverages the URL directly. This means it doesn't support dynamic `href` use.
You need to replace the dynamic `href` with a direct path in the `next/link` component. Here's a before and after comparison of what your code should look like:
In the revised code, the dynamic part of the `href` (`[slug]`) is replaced directly with the actual value (`1`), which simplifies the `href` and makes it a direct path.