For OBJ you can easily copy the item and turn off the other shading groups but for Alembic - that is now always reference - you CAN copy the GeometryAbcMesh and select shading groups there but I'm afraid that will cause problems because the copies are not in the Alembic context anymore.
It seems it is possible to do that with Alembic Bundle but that is not very effective as there is no 'reload' on that so if you have a lot of other resources, you need to do Resync Resources just to update one of the Alembic Bundles and that can take a lot of time. Also as Alembic Bundle cannot separate objects, the Alembics need to be created specifically for that purpose (each object in separate Alembic file) to avoid mess.
So what is the recommended way to create point clouds on shading groups for Alembic objects nowadays?

Thank you!