curl --request GET \
  --url https://api.kinsta.com/v2/sites/environments/{env_id}/themes \
  --header 'Authorization: Bearer <token>'

{
  "environment": {
    "id": "54fb80af-576c-4fdc-ba4f-b596c83f15b2",
    "container_info": {
      "id": "54fb80af-576c-4fdc-ba4f-b596c83f15c3",
      "wp_themes": {
        "data": [
          {
            "name": "twentytwentythree",
            "title": "Twenty Twenty Three",
            "status": "active",
            "version": "1.0.0",
            "update": "available",
            "update_version": "1.0.1",
            "update_status": "updated"
          }
        ]
      }
    }
  }
}