Warning: English is not my native language, so I will do my best to explain the origin and solution of the noise in the car.
After months of trial and error and taking the car to the dealer 3 times, I discovered that the noise is not coming from the back of the car as it seems, but from the front. To find out, I lubricated each rubber component of the front suspension one by one with a silicone based spray oil. When it was the turn to lubricate the upper suspension mount, the noise increased dramatically.
I waited until the silicone oil had dried, and applied a motorcycle chain lube and the noise finally disappeared. Now it's been 2 weeks totally free of noise.
I attach a photo where I indicate with a red arrow the points where the lubricant should be applied, which corresponds to the drainage of the upper suspension mount. I also indicate with green arrows where the entire visible rubber contour should be lubricated. It is important to use a motorcycle chain lubricant that is compatible with oring chains, so that the suspension rubber is not degraded. I used a Liqui Moly "KettenSpray" which is liquid when applied, so it can get in between the little spaces, but then it dries out. If someone thinks it's necessary, I can post a picture of the lubricant I used.
I will also let the dealer know the source of the problem so they can check it more thoroughly and determine if any suspension components need to be replaced or if lubrication is sufficient.
I hope this will help someone solve this problem, as it almost drove me crazy.
Regards,
RSM.