I want to set DuckDuckGo as the default search engine for new users, and allow each user to switch back to Google, if desired.
But .mozilla/firefox/<profile id>.default-esr/prefs.js hard-codes browser.urlbar.placeholderName to Google, so setting it in /etc/firefox-esr/my_settings.js won't work. The new users are created on demand (LXC), so it is not an option to set this manually in each user's user.js or similar. Can I customize prefs.js and where does Firefox take it from? I cannot find it in dpkg -L firefox-esr | grep js and in /usr/lib/firefox-esr/{,browser/}omni.ja. Or is there another configuration file to try?