As mentioned in my previous post, due to a bug in Mac OS Sierra (which I have filed using apples bug reporter), port 8843 on the owncloud server must point to owncloud, which is possible on my Ubuntu host with Okay, finally I have managed to get things working here. So maybe this applies to Address Book/Contacts? It seems that macSierra is now using the same ports as Mac Server for Calendar. I do not know how or if this can be done for CardDAV.
Otherwise each client seems to have to configure Calendar on macSierra to explicitly use port 80 (or 443). Is there a way to configure Apache2 to Listen to other ports besides 80 & 443? That would resolve the problem on the server side. I know enough about Ubuntu Linux to use the ownCloud "Preferred Installation Method". (Also port 443) Notice that it also says ports 8800 & 8843 are used for "Address Book Service". It says port 80 is used for Calendar & WebDAV, which is the port ownCloud expects Calendar connections will be received. I do not use CardDAV, but I think there may be a similar problem. (Intranet so I am not concerned with SSL or m-i-m attacks.) So in the macSierra Calendar app, when I "Add a CalDAV account" I use "Account Type: Advanced" so I could specify "Port: 80".
Was JBOSS HTTPS in Mac OS X Server 10.4 and earlier. I found in "TCP and UDP ports used by Apple software products" at thatĨ443 TCP iCal service (SSL) - pcsync-https Mac OS X Server v10.5 and later. Unfortunately I do not have copies of the logs, but I saw when macSierra Calendar was attempting to contact ownCloud, it was doing so on :8443 (TCP port 8443). No matter what I did in ownCloud9, I got "Unable to verify."