Trickplay thumbnails required, but not provided by Vimeo feed

Hello.

I'm building my first Roku channel app and I am hitting a block. Roku's certification requirements mandate thumbnails for trick play in all VOD over 15 minutes long. All my app's content is hosted in a Vimeo showcase which provides the content feed. However, I'm not finding any trick play thumbnail URLs in this feed. Each entry looks like this:

    {
      "id": "417698928",
      "title": "Title",
      "shortDescription": "Short description",
      "thumbnail": "https:\/\/i.vimeocdn.com\/video\/thumbnailURL",
      "releaseDate": "ISO timestamp",
      "genres": [],
      "tags": [],
      "content": {
        "dateAdded": "ISO timestamp",
        "duration": 777,
        "videos": [
          {
            "url": "https:\/\/player.vimeo.com\/external\/videoURL",
            "quality": "FHD",
            "videoType": "HLS",
            "bitrate": null
          }
        ]
      }
    }

I'm surprised that this isn't something included in the Vimeo feed itself, given that it essentially makes Vimeo Showcase impossible to use as a plug-and-play content feed for any public Roku app with moderately long-form content. Is every public app with content over 15 minutes long that uses a Vimeo Showcase also using some third party service to inject trick play thumbnails into their feed? Or generating thumbnails manually for their content and uploading it to a CDN/S3 instance?

Just want to sanity check that I'm not missing something simple before I do a bunch work and pay for additional services/hosting.