IIRC, Copenhagen interpretation has the observer as "external" to the system they are observing? Which would be an inaccurate interpretation, because the observer as well as the observed system are both "internal" to one universe, which itself is described by one overall wave function, so the observer is not external but is entangled with their own observation, as in the Everettian interpretation. Or, to paraphrase Sean Carroll, Copenhagen interpretation may be popular but it is not a full theory of quantum mechanics.
