Comment 2 for bug 1852097

Olivier Tilloy (osomon) wrote :

The Google calendar provider used to be installed by the xul-ext-gdata-provider binary package, but it's nowadays an empty transitional package. It was removed in version 60.0 (see https://bazaar.launchpad.net/~mozillateam/thunderbird/thunderbird.bionic/revision/446), so this is not a regression.

You can install it from addons.thunderbird.net: https://addons.thunderbird.net/thunderbird/addon/provider-for-google-calendar/ (the version there should be compatible with thunderbird 68.2.1.