You’re right that it does work for 5.6, that’s the last test I did. In the older versions when I tried some things only worked with subsequent unreal version updates. Unfortunately the gltf fixes only seem to be included in new unreal versions. Perhaps you can upgrade your project?
And my glb did have both. But I think we have experienced the same and 5.6 seems to have the most complete version of gltf import.
But again just for sanity check make sure the morph/shape key animations are actually part of the skeletal animation sequence and not a separate sequence that is attached on the mesh instead in blender ( that is if you are using blender, in what are you writing the exporter? ).