Break up your long tasks. One way to yield to the main thread using a combination of a Promise that resolves with a call to setTimeout.

yieldToMain.js

// Based on: https://web.dev/optimize-long-tasks/
window.yieldToMain = function yieldToMain(task) {
  return new Promise(resolve => {
    setTimeout(() => {
      task && task();
      resolve();
    }, 0);
  });
}

// await yieldToMain(...);

I was wondering, wouldn't be queueMicrotask of help?