Because you have an NVidia GPU, the system "helpfully" added two repos:

openSUSE-repos-Leap
openSUSE-repos-Leap-NVIDIA

This created a repo service that caused duplication of repos with identical URLs.
If you desire to keep using this service, you need to remove the duplicates. If
you would rather keep things as they used to be, remove and then lock those two
packages.

AMD and Intel GPU users don't get either added automatically, thus manage repos
the old-fashioned way - I think. It may be that all new installations get
openSUSE-repos-Leap automatically, but it isn't required.

If like me you don't like the long-winded default repo names and change yours to
more concise names, then you need to use the traditional manual management method.

So what does openSUSE (dir:/usr/share/zypp/local/service/openSUSE): [openSUSE:repo-oss|http://cdn.opensuse.org/distribution/leap/15.5/repo/oss] have to do with nvidia? I now don't have duplicate nvidia repos but still get that error.

Mark