openSUSE does support FlatPak, just follow the Wiki entry. There is also a wiki entry about SteamBlender is in the repositories. Also keep in mind that they stance about multimedia codecs is the same as Fedora. Please consusult this wiki entry for more information. I have to say that openSUSE Tumbleweed is a fantastic distro. It is rolling release, but it is also using OpenQA to make sure nothing breaks during updates. Hope this helps.