For Linux look here (addon description):
> For MacOS & Linux users: Use left or middle mouse button due to the different right click/context menu behaviour
But the right mouse click for Linux (and Mac) will probably work in Firefox 58. See here for more informations: https://bugzilla.mozilla.org/show_bug.cgi?id=1360278#c113

And because of the unusable pages look here:
> The addon does not work on https://addons.mozilla.org, pure svg pages and internal pages like about:newtab, about:addons or other addon option pages.