For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Printing/openSUSE_Tumbleweed/Printing.repo
zypper refresh
zypper install ink
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Printing/15.6/Printing.repo
zypper refresh
zypper install ink
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Printing/15.5/Printing.repo
zypper refresh
zypper install ink
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/Printing/15.4/Printing.repo
zypper refresh
zypper install ink