GNOME Bugzilla – Bug 777010
"Owncloud" online-account stops working on Nextcloud 11
Last modified: 2017-01-08 15:08:23 UTC
Changes in the dav URLS in nextcloud break integration into gnome (e.g. no calendars or contacts showing up in evolution): https://docs.nextcloud.com/server/11/admin_manual/issues/general_troubleshooting.html#troubleshooting-webdav See this link for further information: https://help.nextcloud.com/t/nextcloud-11-seems-to-break-gnome-integration/6413
Adding the owncloud account "works", i.e. does not produce a GUI-visible error.
Deleting, re-adding the account, AND waiting for a significant time, solved the issue for me. Sorry for the noise.