static get properties() {
    return {
      plan:Object,
    };
  }

 <div class="body"><p class="title">${this.plan.title}</p></div>

<health-check plan='{ "title" : "Solution Architecure",
 "status" : "Approved" }'></health-check>

<health-check planString='{
  "title": "Solution Architecure",
  "status": "Approved"
}'>
</health-check>

class HealthCheck extends LitElement {
  static get properties () {
    return {
      planString: String
    }
  }

  render () {
    return html`
      <div class='body'>
        <p class='title'>${JSON.parse(this.planString).title}</p>
      </div>
    `
  }
}

<my-app></my-app>

class App extends LitElement {
  render () {
    return html`
      <health-check .plan='${{
        title: 'Solution Architecure',
        status: 'Approved'
      }}'>
      </health-check>
    `
  }
}

class HealthCheck extends LitElement {
  static get properties () {
    return {
      plan: Object
    }
  }

  constructor () {
    super()
    this.plan = {}
  }

  render () {
    return html`
      <div class='body'>
        <p class='title'>${this.plan.title}</p>
      </div>
    `
  }
}