For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/shells/openSUSE_Tumbleweed/shells.repo
zypper refresh
zypper install cowsay
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/shells/openSUSE_Factory/shells.repo
zypper refresh
zypper install cowsay
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/shells/15.6/shells.repo
zypper refresh
zypper install cowsay
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/shells/15.5/shells.repo
zypper refresh
zypper install cowsay