Mac OSX Mavericks (2013) printing to a Canon Pixma MG7750 series (2016). All drivers are up-to-date but Firefox, on the same settings, always wastes paper by printing each A4 page on a fresh sheet.

Have noted from Internet that others could not print duplex via Firefox. Have re-set printer config in Firefox but no help. Very frustrating as I send identical instructions to the printer. Firefox has a user-friendly browsing interface but is badly let down by inability to view a mini printed-page preview (like Safari) -- and also no duplex ability.