I just reinstalled my system (with Debian 9), and a new Thunderbird (60.4.0)
I could not connect to the calendar using lightning or to the address book using cardav:
- no error message for the calendar, but it remains empty.
- unable to validate the URL/username/password in cardbook.
I finally found the solution on the mozilla support. I guess that can be interesting to share it here:
I also copy here the solution, given by Fabián Rodríguez:
"I believe this is the CalDAV known-issue, it’s a NextCloud problem. It’s been reported in this issue, there is a workaround:
Go to the config editor (Settings -> Advanced -> General -> Config Editor) Search for network.cookie.same-site.enabled Set it to false
For your own security you should set it back to true once this issue is resolved.
This was also mentioned in the release notes (very bottom of https://www.thunderbird.net/en-US/thunderbird/60.0/releasenotes/ )"