Keeps obsoleting older plugins, prohibiting use of JS Print Setup on Firefox 57 (Quantum)
(safest choice due to continued updates) together with manual .xpi-addon installation, or Firefox Extended Support Release (
can be used to avoid this, while disabling automatic updates for Firefox and for add-ons, at the expense of exposing security risks. It should be technically possible for the Firefox developers to let the user choose to keep using the many older SDK plugins, at a cost of performance loss.
Another solution could be to use the semifree/semicommercial operating-system-based QZ Tray printing software, that can communicate with the webbrowser through Java, at the expense of a couple of additional programmering hours. While this will avoid Firefox-addons altogether, it introduces a Java dependency and it risks small differences between what's the screen content in Firefox as compared to the printed results, depending on whether the direct-HTML or pixel-capture technique would be used.
Installing add-on from .xpi-file in Firefox 52.7.3 ESR or Pale Moon