Hi, the server URLs I used are as following:
https://contacts.icloud.com
https://caldav.icloud.com
Setting up Thunderbird worked like a charm by just adding new calendar/contacts via “auto-discovery”. I just entered the corresponding server URL, my iCloud credentials and app-based password and there it was.
Using Evolution I entered a little more manually, but that was actually just the “secure connection” option.
As I said, I would like to use only the Gnome stock apps, no “overkill” applications like Thunderbird or Evolution but I fail with the setup via Gnome settings.
There I should enter a (general) server URL, CalDAV and CardDAV should be optional.
But unfortunately that doesn’t work, and to be honest I’m not sure which general server URL address that should be. Apple likes to keep quiet about such things. 