Is there a way to setup rule to always self-assign to whoever initated the task?
No, sorry, there’s no rule functionality which allows for that.
Hi @Leo_Li and welcome to the Forum!
Adding to what @Phil_Seeman’s reply there is an existing thread regarding this topic: Allow Rules to assign to whoever created task, not a specific user.. If you haven’t yet, I would recommend you to upvote it!
Have a great week!