Just ignore that “Repository ‘non-oss-updates’ appears to be outdated” message. It is harmless.
As for the repos being a mess – the patches for SLE and the patches for openSUSE don’t see to mix very well at present.
Yes, the advice is to not use “zypper patch”. So you should also avoid Yast online update (does the same as zypper patch). And the desktop update applet will do the same.
Here’s what I have done (and seems so work).
1: I ran Yast online update – just once. There was only one update, which added a couple of repos.
2: I then used “zypper up” to update everything.
3: If I test Yast Online Update, it wants to uninstall LibreOffice or something similar that doesn’t look right. That’s why I am avoiding Yast Online Update for now.
When I use the link you provided, I get a header bar and a side bar with an empty space. Apparently the site wants me to allow scripting (or maybe even a login?). Not all people are fond of doing this.