No, it's not, because "being at rest relative to the ether" only maximizes your proper time in a very special set of cases (and which cases they are is in principle unobservable). The ether cannot explain why proper time is ever maximized for an observer who is not at rest relative to the ether--or, since we don't know which inertial frame is actually the ether rest frame, it is better to say that the ether cannot explain why proper time is ever maximized for two different observers who are in relative motion (it's maximized for each observer between a different pair of spacetime events, but that's how it works--you can't just decree that everyone has to only travel between some fixed pair of events).in LET, the physical mechanism of time dilation is due to the ether
Yes, and as I said, this is true for any interpretation of relativity.Geometry is how spacetime produces time dilation. There is no other physical mechanism.
But this is only true in some interpretations of QM, not all of them.Wave function is how matter produces observable. There is no other physical mechanism.