Empty Contacts add book

By default Thunderbird has no access to your Mac "Contacts". Open your System Preferences > Privacy & Security > Privacy: in the left panel select "Contacts", then in the right panel with the list of apps search for ▢ 'Thunderbird' and set a check mark. Probably you'll be prompted to restart Thunderbird. EDIT: I'm not sure whether this works with Tahoe because of bug 1720257 https://bugzilla.mozilla.org/show_bug.cgi?id=1720257 I cannot test this since I am still running Monterey. If you use iCloud you can create a CalDav address book as an alternative which will sync with Contacts in both ways.