Rated 3 out of 5 stars

Great, but...
In Thunderbird 91, it makes crashing Thunderbird AND the computer ! ! !
In Thunderbird 91, there is the sync addressbook originally. But it doesn't sync groups (only contacts).
Google--4-tbync is able to sync all (contacts and groups). But in TB 91, it makes freeze Thunderbird AND computer for looooonnng time (about a hour and half...).

This review is for a previous version of the add-on (0.2.1). 

Thanks for Your review.

However, as this is the first report of this kind, I'd like to know more about. How many addressbooks did You test with? How many contacts and contact groups?

Please open a specific issue on the GitHub page.

Thanks,
MZ