DAVx⁵ Settings
Choose "Login with URL".
Base URL: https://your.server:8443/ or http://your.server:8080 (see Kopano manual: Configuring CalDAV clients; you don't have to add /<user>/ etc.)
User name and password: your Kopano account
At the moment, Kopano doesn't support CardDAV, so contacts can't be synchronized.