The crux lay in the version of Firefox. To all who run into the same problem while using Leap 15.0 OpenSuse, this finally solved it y system had version 60 of Firefox, while it only ever works from version 63 upwards. Tried after regular (via add-ons in Firefox add-ons menu ) installing, immediately worked. By now you are probably in an asylum trying to regrow hair you ripped from your skull, embittered by the lack of help Linux users were able or willing to provide. You can come out now, retake your place in society, stop the foaming about the gob. All's well that ends well, thank you very much @dev, for the quick response and for ridding me of that linguistic monstrosity, the US " English" dialect, may it rot in all seven hells of legend.