This article explains how to sync Google Calendar with Thunderbird using the Provider for Google Calendar add-on. This process should work with any version of Thunderbird (newer than 52.0) running on any platform.
Sync Google Calendar and Contacts with Thunderbird, without Add-ons
Do you depend on Google Calendar, but don’t want to leave your Thunderbird email client to view it? You’re in luck, because Mozilla’s Provider for Google Calendar add-on lets you sync Google Calendar with the email client with both read and write access.
The first thing you need to do is download Provider for Google to enable bidirectional access to Google Calendar.
Open your web browser and go to the Google Calendar Provider web page.
