@PaulGWebster first here's your feature request thread for CardDav: https://forum.vivaldi.net/topic/53314/contacts-carddav-sync
I don't use multiple caldav servers on the same host so I would have to test this specifically - you seem to have found a workaround in that other thread (and thanks for describing what you did in case someone stumbles across the same issue). Since this is a community forum the thread alone won't trigger any attention from the developers - best write a bug report in which you can also reference the thread, and note the bug number you receive in the thread. That way, if they fix it, you'll get a notification.
@PaulGWebster said in Cannot configure email as both incoming and outgoing require StartTLS?:
vivaldi on its own could be 'the business browser' with all of these features nicely implemented;
I am fully with you here, with all its productivity features, Vivaldi would do good to target small businesses. But even though that would be a steady way to grow, it's also a slow path. Right now focus is on getting pretty much any sort of attention - they claim to have just 2.4M users overall, which is close to nothing regarding market presence. I would hazard the guess that most users trying out Vivaldi do so for personal use, and as such when they use Mail, they will be happy if the contact shows up as they typing a name in the address field, which is the case. But since they have added support for CardDav in the webmail solution, I think it's just a matter of time until we'll see proper contacts management in the client, too (which sadly still means it could take a lot of time).