I finally got Mirage installed, via 1-Click Install, here: https://software.opensuse.org/package/mirage
I had been unable to play .wma music files, but then I found the following note about multimedia codecs (at http://ordinatechnic.com/os-specific-guides/opensuse/opensuse-leap-421-review-supplement):
In addition to adding the PackMan repositories, they must be prioritized over the default openSUSE repositories to prevent a change in package version during updates to those in the default openSUSE repositories. This is important for packages like vlc and vlc-codecs where the PackMan versions, besides being ususally newer, support proprietary codecs and the openSUSE ones don't.
It is also important to be aware of the concept of vendor in openSUSE. If software available from the openSUSE repository has been installed, then the PackMan repository is added, already installed packages can be changed to the versions in the PackMan repositories. This can be done in the YaST Software Management module by viewing packages by repositorym, selecting the PackMan repository, then clicking "Switch System Packages to Versions in this Repository".
I followed those steps (this installed/updated a lot of multimedia packages), then logged out of KDE and logged back in. After that, I was able to play .wma, .ogg, and .mp3 files.
There are a few other little things I'd like to get fixed up, but "Leap" 42.1 is shaping up nicely. Always seems to take a bit of post-installation work to get an openSUSE installation set up like I want it; well worth it, in the end.