It occured to me yesterday evening.
Though knowing the issue of placing displacements on imported objects, I gave it a try.
First, I created a nice cube in Cinema4D, exported it, loaded in TGTP and resaved as tgo.
Loaded this tgo and any displacement killed the mesh.
Then ...
... I started to play around. Stirring and shaking the nodes
Well, as soon as I put into the shader of the mesh the Base-colour-shader, the displacements worked. Even hard displacements.
But only on the upper side of the cube.
This might be, because I deleted the multishader of the mesh, but dunno.
It was time to go to bed then ... but maybe somone wants to give it try or two!?!
Volker Harun