Review for Provider for Google Calendar by Paul
Rated 3 out of 5 stars
It works, but lacks the ability to add an event from an email invite as there is no option in the settings to assign an email to a calendar. I found that adding a standard Thunderbird network calendar using my Google email and the Secret address in iCal format worked better and allowed me to subscribe to all my Google calendars with email invite support.
This review is for a previous version of the add-on (102.0.3).To create your own collections, you must have a Mozilla Add-ons account.