Hi!
According to the Scrum Guide, If the Product Owner or Scrum Master is actively working on items in the Sprint Backlog, they will join as a Developer.
So What Product Owner, Scrum Master do in Daily Scrum?
Below is my opinion, let me know it's right or wrong.
SM and PO can join the Daily Scrum together.
SM observes and makes suggestions for Development Team to properly implement the Daily Scrum, such as take place and are positive, productive, and kept within the timebox.