Rated 3 out of 5 stars

Thank you roonra for the great app G-Hub Lite!! it does much more than the Google Calendar. I love it!!
But hope the developer of this app will update it for the new TB.

Rated 5 out of 5 stars

Add-ons not marked as compatible with Thunderbird 60 by their authors will be disabled.
This can be reverted via preference: extensions.strictCompatibility
So go to Options->Advanced tab->Config.Editor and search for "extensions.strictCompatibility" then change it from True to False by double clicking on it.