plasma-theme-klassik from home:llunak:kde project

For openSUSE Leap 42.2 run the following as root:

zypper addrepo https://download.opensuse.org/repositories/home:llunak:kde/openSUSE_Leap_42.2/home:llunak:kde.repo
zypper refresh
zypper install plasma-theme-klassik

For xUbuntu 12.04 run the following:

Keep in mind that the owner of the key may distribute updates, packages and repositories that your system will trust (more information).

echo 'deb http://download.opensuse.org/repositories/home:/llunak:/kde/xUbuntu_12.04/ /' | sudo tee /etc/apt/sources.list.d/home:llunak:kde.list
curl -fsSL https://download.opensuse.org/repositories/home:llunak:kde/xUbuntu_12.04/Release.key | gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/home_llunak_kde.gpg > /dev/null
sudo apt update
sudo apt install plasma-theme-klassik