Misleading title. Using this with your day to day browser burns out any idea of anonymity.
If you want to be safe, make a bare bone Arch Linux VM and use this extension with GNU Icecat. Also change your DNS from your ISP to something like Quad9.
Does icecat use a custom user config that provides more privacy/security? I see on their page they package it with some preinstalled extensions (JShelter being of interest but only helping to increase the fingerprintability of your browser). All I know about it is that it is a GNU drop-in Firefox replacement (since it is a fork), but it most likely doesn’t enable privacy.resistFingerprinting or many of the other things available in the Firefox config. You will not have anonymity on your proposed setup, nor even using something like the arkenfox user.js which provides much better privacy and security than the loose defaults of Firefox. I would instead recommend Librewolf, or even better Mullvad browser.
