[ScaredToUseName]

This is why whenever I install firefox, I first turn off wifi. Then I go through the settings and disable the ‘studies’ and other telemetry, etc, before switching the wifi back on. That will prevent the having to wait 30 days for the data to be deleted from Mozilla servers with it’s ‘on by default’.

[voytec]

I use ESR with pre-baked policy[0] stored in /usr/lib/firefox/distribution/policies.json before the installation/1st run. Configures cookies, studies, disables logins, credit cards saving, asking for location, promptimg for notifications, studies, pocket, telemetry etc. During 1st run, it installs all pre-defined extensions.

For some reason, changing search engine via policy no longer works, but that can be bypassed by auto-installed extension that changes search engine.

[0] https://mozilla.github.io/policy-templates/

[capybara_2020]

Did you check and see if this feature i.e. the "Website Advertising Preferences" is turned for you right now?

I have all telemetry turned off but when I went and checked this "feature" was enabled by default with no notification it had been added.