“컴포넌트가 gjs로 작성되었습니다” - 하지만 실제로는 아닙니다

If you use gjs for your FeedbackStream, then I think it should work. So it would be something like

export default class FeedbackStream extends UserStream {
  <template>
    Your custom template here 
  </template>
}

I think mixing hbs/gjs in the same component inheritance chain is unlikely to work too well.