My new Macbook Pro M1 Max is very quick at all tasks except when it comes to importing images from an SD card. It takes Lightroom Classic anywhere from 30 seconds to two minutes to actually display the preview of the photos, the slowest it's ever been on any of my computers, ones with much less power than what I currently have.
I am simply bringing this to the attention of Adobe developers.
Could it be that you are using a very old and thus slow card? I have a MBP M1 Max too and I do not see this problem. Videos may take a bit of time to show a preview, but photos show a preview instantly.