After a year ...
Almost every device of this type has an SD slot. At Alpine it is almost always hidden
Spoiler: manual
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[Only registered and activated users can see links. ]

Yes, the maps are updated via USB, and it is possible that the card is in the device itself. I don't see why you wouldn't open it, it is not a rocket science
I was told a long time ago that the slot is under the display, but rarely does anyone have the opportunity to check such information.