Thanks for your reply. Tableau Catalog looks interesting.
On this "Tableau Catalog automatically ingests all of the data assets in your Tableau environment into one central list." -> does it only index datasources/databases currently in Tableau workbooks on Tableau server?
The Tableau Catalog is a data-management add-on, which depending on your license model, may be an extra cost. Keep that in mind.
Data Catalog only provides information about the Tableau ecosystem, not other vendor platforms.