Firefox previous print interface window: For now you can revert to the previous interface by setting a pref to false on the about:config page. print.tab_modal.enabled = false

You can open the about:config page via the location/address bar. You can click the button to "Accept the Risk and Continue".

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thanks "jonzn4SUSE", that solved the immediate problem.

Now, how do we get Mozilla to fix errors like the fact that it prints duplex with the pages upside down. Their simplistic menu doesn't allow you to control this non-standard technique.

Does printing once without duplex (a single page to your printer), then printing again with duplex turned back on fix things?