How to enable closed captions by default with OpenPlayerJS / video.js?

Question

I have very simple function to start playing audio in OpenPlayerJS which is a fork of video.js. The track for closed caption is same name as the mp3 file passed, and the function correctly adds it.

I want to have the caption mode enabled by default. Cannot find the option to enable it by default in player loader arguments. It does not get enabled by calling track.mode = "showing" as explained here https://developer.mozilla.org/en-US/docs/Web/API/TextTrack/mode

function play(sound) {
  let id = document.querySelector('.op-player').id;
  let player = OpenPlayerJS.instances[id];
  let captions = stem(sound) + '.vtt';

  player.src = { src: sound };
  player.addCaptions({ src: captions, kind: "subtitles", srclang: "en", label: "English" });
  // https://developer.mozilla.org/en-US/docs/Web/Events#media
  let track = document.querySelector("track").track;
  track.mode = "showing";
  
  player.play();
}

What am I doing wrong or missing? I just want this "CC" option to be enabled automatically: