Hi Cosimo,
uBlock Origin can already be found on IceCat's extensions page
(https://directory.fsf.org/wiki/IceCat), at the bottom of the list.
As for the add-ons page on gnu.org, the top of the page explicitly
states that "this page has been deprecated in favor of two pages in the
Free Software
I'd like to point out the extension uBlock Origin:
https://github.com/gorhill/uBlock
As you can see from the website it is explicitly released under the
GPLv3, but it's not included in your list:
https://www.gnu.org/software/gnuzilla/addons.html .
I strongly suggest you include this
