Front control arm rear bushes have been replaced by Powerflex PFF19-1102BLK. This did not solve the problem.
It did give a better steering, without any adverse effect.

Then I replaced the lower gearbox mount by a Vibra-Technics FOR620M. This solved the problem for 90%.
It gives some more vibrations inside the cabin. Also the noise at highway speed seems to have increased.
But so far I can live with that. These inconvenients might perhaps get better over time. Some bushings tend to bed in after a while.