GUI-oriented folks can also install add-ons with a mouse, by dragging the .xpi file from the desktop or a graphical file manager, and dropping it onto a running icecat window
i just installed "dark reader" from the mozilla website and it installed as expected - most likely, the OP's self-compiled package is rejected because it has no signature so, there are four options (in order of preference): * convince the gnuzilla devs to package that add-on for everyone * register for a mozilla dev key and submit the self-compiled package to mozilla for signing (that is the standard procedure, if you wish to redistribute) * disable signature checking, as mark suggested, install the unsigned package, then re-enable signature checking * simply install the package from mozilla
