Hello.
My camera gives a different lens name:
$ exiv2 -pt DSC_0174.nef | grep -ai lens
Exif.NikonLd3.LensIDNumber Byte 1 Nikkor AF-P 18-55mm f/3.5-5.6G DX VR
Whereas in the slr-nikon.xml it is named (in <model>) "Nikon AF-P DX Nikkor 18-55mm f/3.5-5.6G VR" and Darktable doesn't recognize this lens.</model>
Please, duplicate "Nikon AF-P DX Nikkor 18-55mm f/3.5-5.6G VR" with name (in <model>) "Nikkor AF-P 18-55mm f/3.5-5.6G DX VR".</model>
Camera Nikon D3400.
Sorry but problem was disappeared after update. Please close this ticket.
Best regards