For openSUSE 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deneb_alpha:branches:openSUSE:Tools/openSUSE_15.6/home:deneb_alpha:branches:openSUSE:Tools.repo
zypper refresh
zypper install osc
For openSUSE 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deneb_alpha:branches:openSUSE:Tools/openSUSE_15.5/home:deneb_alpha:branches:openSUSE:Tools.repo
zypper refresh
zypper install osc
For SLE 15 SP6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deneb_alpha:branches:openSUSE:Tools/SLE_15_SP6/home:deneb_alpha:branches:openSUSE:Tools.repo
zypper refresh
zypper install osc
For SLE 15 SP5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deneb_alpha:branches:openSUSE:Tools/SLE_15_SP5/home:deneb_alpha:branches:openSUSE:Tools.repo
zypper refresh
zypper install osc