bug#47500: Hello, I would like to use the Dark Reader extension with IceCat

[bill-auger]

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