Lens correction module (Darktable 3.8.1) does not automatically apply the correction since it does not find the objective as described in exif data of the pictures from the camera.
Looking in the /var/lib/lensfun-updates/version_1/slr-tamron.xml (Ubuntu 20.04) the description more similar to my objective is:
Tamron SP AF 17-50mm f/2.8 XR Di II VC LD Aspherical (IF)
while in exif data is:
TAMRON SP 17-50mm f/2.8 Di II VC B005.
So I added a “new” lens in the file slr-tamron.xml with the right description as below:
TAMRON SP 17-50mm f/2.8 Di II VC B005
Now it works fine and lens correction apply the automatic correction.
The drawback I see is that when lensfun is updated, I will have to remember to add the “new” lens again. Is this the right way of work around the problem? Someone of you coped with this problem? How did you manage this problem?