I see the Printable View option on reports is marked for just a Future version on the road map. It would be nice if SFDC would just add a button in Lightning for some of the standard features in Classic not available yet in Lightning, like printable view, so a user could click this button in Lightning and open the report in classic for printable view and when the user clicks on something else it takes them right back to Lightning. Its very frustrating for users and admins to have to use the switch to option to do these things.  Its hard to keep users in Lightning when they keep having to switch back to Classic to do things not available yet in Lightning and users lose motivation to switch back to Lightning when the speed is faster in Classic and everything they need is there.  It does not remember what record you were on when you change, it always takes you to the home screen which adds to the frustration. I know it takes time to migrate over all the standard functionality, but make it easier for users to access standard things in Classic not available in Lightning yet.