Hi,It's not possible. When importing from a connected camera or SSD, Copy as DNG and Copy are the only options.Add is only to import photos to the Lightroom catalog while keeping the files in their original location.Michael
I think they disallow Add from an SD card because it’s assumed to not be a permanent location. If the photos are added from a location that could disappear, such as when an SD card is reformatted, then the originals would be gone forever. They don’t appear to support the uncommon case of using an SD card as long term storage for master images.
They really want you to copy the photos from SD to a location that is unlikely to change, such as a hard drive.
You can use an SD card on a Mac and use ADD or MOVE if you format it in the computer and NOT use/format it in the camera where the DCIM folders will be created as it is treated like a drive. I have used an SD card in this way to Export as Catalog to the SD including the Negatives so I can take the SD card to another Mac to do some editing on a few photos with another person. I have copied other photos to the SD and imported them. LrC actually works pretty well from an SD card if the card is relativly fast. I would not recommend this for general use though. From what I understand, this does not work on Windows.