Review for Provider for Google Calendar by Andyross
Rated 5 out of 5 stars
As of Thunderbird 78.8.1, the calendar now automatically shows whenever you start Thunderbird. You no longer have to go to the settings and hide/show it.
Not too much to say about the add-on itself other than it works as expected.
To create your own collections, you must have a Mozilla Add-ons account.