I'm not sure whether Iceweasel addons should be added as packages or not. I can find some addons from the repos (e.g., ublock) and I feel that's better than downloading addons from random webpages (see, for instance, https://wiki.debian.org/Mozilla ). Anyway, here's some info:

Zotero is the only research tool that automatically senses content in your web browser, allowing you to add it to your personal library with a single click.

FSF: https://directory.fsf.org/wiki/Zotero_client

Download: https://www.zotero.org/download/

GitHub: https://github.com/zotero/zotero (I'm not sure if this is the Firefox extension or stand-alone client, but I hope it's the Firefox extension)

AURs only include the stand-alone client.