It was broken for me also and comments from #3 and #4 helped. Calendar is very important functionality and sudden disappearance was very problematic. May be work with Mozilla and ask them to update documentation for Ubuntu so that others facing this problem will have a quick solution.
I certainly did not know about the lightning package and always have installed from thunderbird. Another alternative could be update manager to warn people that it can break functionality. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to thunderbird in Ubuntu. https://bugs.launchpad.net/bugs/1797945 Title: Lightning incompatible with Thunderbird 60.2.1 Status in thunderbird package in Ubuntu: Confirmed Bug description: Hi Today I got the update from Thunderbird 52 to 60.2.1. Unfortunately Lightning doesn't work anymore. Thunderbird reports that Lightning is incompatible with Thunderbird 60.2.1. Regards, Ettore -- WORKAROUNDS: Until this is fixed (as per the problems listed in #25), pick an answer that works best for you (English vs. other languages) at https://askubuntu.com/questions/1084059/latest-update-to- thunderbird-60-2-1-on-18-04-lightning-calendar-missing . To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1797945/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp

