So i also tested to create a app-password as well. It also works not.
I tested also the WebDAV config in the browser. There comes the following message: "This is the WebDAV interface. It can only be accessed by WebDAV clients such as the ownCloud desktop sync client."
Unfortunately there is no single solution to this as most issues causing these are related to various server misconfigurations. However there is a large FAQ available here at the forums showing all known information how to configure / fix your environment: