If you want to use Firefox sync IIUC you can define a new pref services.sync.prefs.sync.dom.private-attribution.submission.enabled. However this has always been flakey in the past for me. (I think maybe the sync prefs themselves don't sync?)

Now I install an organizational policy that sets the prefs. I use NixOS to apply this and it looks like this:

    environment.systemPackages = [(pkgs.firefox.override {
      extraPrefs = ''
        lockPref("dom.private-attribution.submission.enabled", false);
      ''
    })];

I think this is just creating a `prefs.js` file under the hood, so you should be able to replicate on other systems that you manage.

Edit: This is creating a lib/firefox/mozilla.cfg. IDK how exactly this applies to other distros.

Basically, you need to create a `user.js` file in the root folder of your profile, you can find/open the profile folder using about:profiles or about:support (default path is `~/.mozilla/firefox/${profile-name}/user.js`). You can sync it however you like, e.g. upload it to your dotfiles repo and symlink with stow, etc.

The syntax is: user_pref("dom.private-attribution.submission.enabled", false); // Disable Privacy-Preserving Attribution

You can find a lot of examples and "documentation" on https://github.com/arkenfox/user.js