Isn't that more dependent on your distro than anything else? On openSUSE Leap 42.2, my default is 3.0.1.1, and I could add the less-tested but realistically fine KDE:Extra repository for the latest version. Fedora seems to be shipping 3.1.1 as well. Arch and openSUSE Tumbleweed are also on 3.1.1.