The only way to disable PB mode is via a policies.json, I assume that this works the same on Flatpak and Snap.

• https://support.mozilla.org/en-US/kb/customizing-firefox-using-policiesjson
• https://mozilla.github.io/policy-templates/

Ive tried that, but no dice. I the put policies.json file in /usr/lib/firefox/distribution, and this is in the file: {

 "policies": {
   "DisablePrivateBrowsing": true
 }

}

Is there anything I did wrong?

Looks good to me assuming that that is the correct Firefox installation folder. You can check this in about:support under "Application Basics -> Application Binary".

You can open the about:policies page to see if policies are active and if errors are reported.

• https://support.mozilla.org/en-US/kb/see-active-policies-firefox-enterprise

Thank you! It wasn't under /usr/lib/firefox/distribution, and instead under /app/lib/firefox/firefox-bin