How do I add a Carddav account on my Q10?

I tried and failed to add a carddav account on my Q10. That was almost 2 years ago.

Now with 10.3.1 I decided to give it another try, hoping whatever issue there was had been solved by now.

However, when I enter the information, it checks them and after a little time comes up with the error message "An unexpected problem occurred. Some features may not be working correctly."

In the end, I can't add the account.

I rebooted the phone several times, the problem persists. I thought, the webmail provider might be at fault, the information might be incorrect but I tried it with an iPhone and it worked straight away.

Any ideas?