Edit: perhaps best to refer to the linked topic Legal Tools Plugin and specifically the extended download?
If you install the Data Explorer official plugin, when you create a query you can search for ‘user_id’ and get a drop-down of all tables with records like that. Maybe this is a starting point?
I see about 75 tables with user_id columns, if I read it right. (“userid records” is the arbitrary name I gave this new query.)
