Both Thunderbird and Firefox ESR have been upgraded to Version 68 on my Windows machines a long time ago, but I still have Version 60 on Ubuntu. PPA is
41 Answer
Discovered the Ubuntuzilla repository has the latest versions of both Firefox ESR and Thunderbird, so I deleted the versions from the OP PPA and replaced them with those. Had to move the profile files to different directories because they had different names, but that was easy enough. All up to date the the current security patches again.