I would try setting within about:config ~ privacy.trackingprotection.enabled to true. It is the most basic of tracking protection. Other addons are

https://addons.mozilla.org/en-US/firefox/addon/ghostery/

https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/ (when option menu appears turn all options to on for full protection)

https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

https://addons.mozilla.org/en-US/firefox/addon/adblock-edge/

https://addons.mozilla.org/en-US/firefox/addon/privacy-badger-firefox/

https://addons.mozilla.org/en-US/firefox/addon/disconnect/

To -- LostGod -- [SOLVED] I thank you for your speedy reply but I fear you have misunderstood the problem. The Add-on "Better Privacy" specifically deals with LSOs, not normal trackers. In Linux, these are stored in a sub-directory of the hidden directory (dot)macromedia. These LSOs are commonly used by on-line gamers, etc. to hold their information between sessions. They are not removed by the FF setting of "Preferences > Privacy > Delete history on exit". So, I have Ad-block and Ghostery installed and these are still working OK and deal with the normal trackers. This problem seems to have arisen/been spotted later yesterday (UK time). This morning, I visited the Better Privacy web site and have found a note stating that they are aware of this problem and are working on a fix, so I've just got to be patient. I have marked this matter as "solved".

My thanks to you again for your attempted help. -- Best regards --

beric