Before the changes to how duplicates are displayed earlier this month, it was possible to get data on duplicate questions and their "originals" out of SEDE by parsing the automatically inserted string. It wasn't pretty (or fast), but it worked, well enough to verify information provided by the team, and even correct it: 1, 2.
The newest SU data set is February 10, well after the changes went live. One question closed as duplicate in that time frame is this one, and there's nothing in Data Explorer linking it to the original: The duplicate message is no longer a prefix edited into the post, and therefore no longer queryable at all:
DuplicatePostIdor something like it pointing to the linked question
- There's nothing useful in
PostHistoryfor the closed question other than it was closed and by whom
Votestable has nothing either, and doesn't even mention a reason (like duplicate, off topic, ...)
Please provide a way to determine duplicate question relationships in Data Explorer again.