I had the exact same issue; I've always not used iCloud or DropBox on this particular Mac (10.13.6). I unchecked HandOff and made sure no files are linked to iCloud as Claudio Escobar but the pop-up persist. I then remove ICloud Device from Finder's Favorite then the pop-up goes away - not entirely sure why perhaps that has to do with the file system in 10.13.6.
I had the exact same issue; I've always not used iCloud or DropBox on this particular Mac (10.13.6). I unchecked HandOff and made sure no files are linked to iCloud as Claudio Escobar but the pop-up persist. I then remove ICloud Device from Finder's Favorite then the pop-up goes away - not entirely sure why perhaps that has to do with the file system in 10.13.6.