Hello!
Need permisions report from Sharpoint, whitch users have access to folders. Full report, permisions tree about all folders on the server (not only about main folders). I have never found such an opportunity
You need to write custom script for it.
For SharePoint On Premise
https://gallery.technet.microsoft.com/office/SharePoint-Access-Report-ac5e8235
This script generate the report for the permission on the site collection, you can use the part of it to browse thru the select document library.
However they cannot know about AD Group users which is big limitation on it
Regards, Sachin