For openSUSE Leap 42.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Cloud:OpenStack:Rocky/openSUSE_Leap_42.3/Cloud:OpenStack:Rocky.repo
zypper refresh
zypper install conntrack-tools
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Cloud:OpenStack:Rocky/openSUSE_Leap_15.1/Cloud:OpenStack:Rocky.repo
zypper refresh
zypper install conntrack-tools
For openSUSE Leap 15.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Cloud:OpenStack:Rocky/openSUSE_Leap_15.0/Cloud:OpenStack:Rocky.repo
zypper refresh
zypper install conntrack-tools