Unique Lookup values across a grouping

I can’t figure out how to summarize a count of unique records across a grouping, either with a rollup or formula or even with a pivot table.

I’ve created a sample base here with creator permissions.

On the Interests tab, you’ll see the Categories I’m looking to count unique People across. Each of the groups should have 4 unique People. How do get that to show up somewhere?

Thanks!

This topic was solved and automatically closed 15 days after the last reply. New replies are no longer allowed.