IOS LAN SAMBA share access A Western Digital MyCloud NAS is pinned on a LAN: is there any native IOS 12.X functionality that enables users to discover LAN-SAMBA resources and browse them (like OSX Finder)?
No, there's no native functionality included with iOS for that purpose.

You can download an app to get the functionality you describe. For example the free "FE File Explorer: File Manager" app from Skyjos Co.