I’m also experiencin the same Problem and the graphic processor is off. Last light it took me 9 hours to import 3587 pictures. Also how can I stop Lightroom from building previews while Importing?
I would prefer to import, delete pics I don’t what and then build previews.
Equipment: 2018 MacBook Pro 15“
Lacie 4 Gigs USB C external HD
USB 3.0 SD card reader
In the Import dialog use the "Embedded & Sidecar" option. Lightroom will use the embedded jpg from the raw file as the initial preview. At some time later it will modify the previews as you work with photos.