I went to login to ownCloud on my iPhone 8 with iOS 13.1 today. It prompted me to download a NEW ownCloud app. So I did.
I put in my ownCloud site URL and user & pass. It will not take the login. It just shacks like it is a bad login.
I have confirmed the username and passwords is the same one I use for my web interface.
Not sure what to try next if the OLD app is being phased out.