Some ideas are:
- You branch off into another timeline and your actions make no difference to the previous timeline
- You’ve already taken said actions but just didn’t know about it so nothing changes
- Actions taken can have an effect (so you could suddenly erase yourself if you killed your parents)
- Only “nexus” or fixed events really matter, the timeline will sort itself out for minor changes
- something else entirely
Probably “read only”/neighboring dimensions. Can’t change the timeline you came from. If you could there’s just no way there wouldn’t be evidence of people doing it.
But otherwise I guess “all changes due to time travel have already happened” as incompatible with free will as it is.