Setting up a new calendar in Thunderbird with the lightning extension installed seems relatively straight forward. (create new calendar, chose "on the web", select "caldav", ... ) However, the process then requires the URL / webaddress of the icloud calendar with which I seek to sync. How do I find this? What are the next steps in the process, including using 2-factor authentication and an app specific password generated via apple/icloud? Can I use the same app specific password I used for setting up icloud mail in Thunderbird ? or do I need a second app specific password? Once all setup and working, can I switch off 2 factor authentication in icloud without harming the by then working sync process with icloud? thanks for your help!