Not very useful for portability unless you plan on scraping the metadata from each URL.

For European residents, if you request a copy of your data (GDPR), you get your playlists as JSON. Granted, the data is not very elaborated, but it's a start:

  {
    "name": "Spotify Playlist Export Test",
    "lastModifiedDate": "2019-02-15",
    "tracks": [
      {
        "trackName": "Sabotage",
        "artistName": "Beastie Boys",
        "note": null
      },
      {
        "trackName": "Unknown Track",
        "artistName": "Unknown Artist",
        "note": "LOCAL FILE"
      }
    ]
  }