Incorrect (inline template inside a route class):

// app/routes/posts.gjs
import Route from '@ember/routing/route';

export default class PostsRoute extends Route {
  model() {
    return this.store.request({ url: '/posts' });
  }

  <template>
    <h1>Posts</h1>
    <ul>
      {{#each @model as |post|}}
        <li>{{post.title}}</li>
      {{/each}}
    </ul>

    {{outlet}}
  </template>
}