You do get blank-ish MFU Ev1 cards. They of course have the UID and internal bytes written in the first 3 blocks, plus the configuration blocks at the end. The remaining space in the middle is blank with only 0s.
Darkside and Nested attacks are Mifare Classic exploits, not Mifare Ultralight.
You should be able to dump the card, understand what data has been written and the configuration blocks. To completely copy it you would need a magic MFU card which can change its UID to be the same as the original.
This isnt something Ive dont too much with so Id be happy to hear any findings you have.