For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:andythe_great:branches:openSUSE:Factory/openSUSE_Tumbleweed/home:andythe_great:branches:openSUSE:Factory.repo
zypper refresh
zypper install labplot-kf5
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:andythe_great:branches:openSUSE:Factory/openSUSE_Leap_15.1/home:andythe_great:branches:openSUSE:Factory.repo
zypper refresh
zypper install labplot-kf5