I saw that a recent question was closed as a duplicate, however no link to the duplicate question appears. Which question is that? Is it possible that the question was closed as a duplicate of itself?
It's a serious bug, but already reported on main meta and devs are looking at it:
Here's hoping it'll be fixed as soon as possible.
In the meantime, you can at least figure out the dupe target by checking the list of Linked questions in the sidebar, which is still operational.
EDIT: this bug has now been fixed. I reopened and re-closed the question that inspired this meta post, and after that Yaakov Ellis (dev) fixed it retroactively too:
I have just run a backfill to fix all occurrences of this across all sites on the network (332 instances of it happening on the entire network that needed to be fixed, including 216 on SO). So if this appears for any questions closed after 2020-4-6 14:08 UTC then it means that the issues is still happening.
Issue with the edit/original screen for mods and gold tag users has also been fixed.
If you do see any other such questions, feel free to raise a moderator flag asking for a reopen and re-close so that the link will appear properly.