You said you have "newly installed Trisquel 9", later it's revealed that you
have "privacy apps collection" installed. You added stuff on top of default
Trisquel install.
Anyway I found on the web what may be a solution:
in address bar type about:config
hit enter
search for security.enterprise_roots.enabled and set it to false
If this setting is locked, look for for Autoconfig files in:
~/.mozilla/abrowser/YOUR_UNIQUE_NAME.default/
A file named prefs.js is normal. Any other script file in this folder is
suspicious and could be used to lock preferences. Remove any such files to a
neutral location for further analysis at your leisure. You can rename the
file with a .txt extension and examine it for the name of another file that
contains the locking code.
Then try again to set to false security.enterprise_roots.enabled
