For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:e_dimas/openSUSE_Tumbleweed/home:e_dimas.repo
zypper refresh
zypper install kf6-oxygen-icons
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:e_dimas/openSUSE_Slowroll/home:e_dimas.repo
zypper refresh
zypper install kf6-oxygen-icons
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:e_dimas/16.0/home:e_dimas.repo
zypper refresh
zypper install kf6-oxygen-icons