Hi @Werner Stinckens​ , yes, the wording leaves a lot of questions. I'm assuming it means you can't use externally managed tables (in Unity) whose location is in a mounted directory.

Since the post I created a new workspace, assigned the unity metastore to it and checked that mounts still operated (for things not in Unity Catalog). This seemed to work but I must say my testing wasn't extensive. It would be nice to get an official position from Databricks. I didn't test the feature store tables so I'm still not sure what this means for these.