Comment 28 for bug 1945368

> And back to the Google Calendar
I'm humbly suggesting, that why release a NEW TB version without a MESSAGE warning Lightning users to disable Google Provider if thats what is needed to make it work?!

An updated version of the provider is in the making and it is now marked by the compatibility check add-on [1], that it is currently not compatible with TB91. So if you install that compatibility check add-on in your TB78, it will check for you if it is safe to update to TB91 or not.

[1] https://addons.thunderbird.net/addon/addon-compatibility-check/

General information: We will not be able to manually "convert" calendars created/managed by the google provider add-on (which is using a proprietary google API to get all the data, including tasks) to CalDAV calendars managed by Thunderbird directly (which does not support tasks, because Google does not provide that info via CalDAV). If you want to switch from one method to the other, you will have to do that on your own:
* Remove old google calendars
* Remove provider add-on
* Add google calendars as CalDAV

This is not really related to the upgrade from TB78 to TB91.

> Even with OAuth in my experience, the ' Less Secure App ' BS is ALWAYS NEEDED !

That is really not true. See the attached image below.