An ether that can be pushed against is an ether with mass. There's a sibling comment in this thread talking about dark matter as a candidate for an ether and the problems with such a concept.

An ether that can be pushed against is also an ether that has a frame of reference, and that frame of reference is unlikely to be one that is extremely favorable to use of the EMDrive as a drive.

An ether that is in some way massless or frame-of-reference-less but still can be pushed against is a fundamental rethinking of physics.