Property ‘dataset’ does not exist on type ‘EventTarget’

Problem is here Element, document, and window can be an EventTarget. You should detect your EventTarget if is an element. So in your case below code should work

linkProvider = (ev: React.SyntheticEvent<EventTarget>) => {
  // If event target not an HTMLButtonElement, exit
  if (!(ev.target instanceof HTMLButtonElement)) {
    return;
  }
  console.debug('ev.target', ev.target.dataset['ix']) 
}

In the short way

linkProvider = (ev: React.SyntheticEvent<HTMLButtonElement>) => {
  console.debug('ev.target', ev.currentTarget.dataset['ix']) 
}

And also i added example here