For openSUSE Factory+GNOME Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/GNOME:Apps/openSUSE_Factory+GNOME_Factory/GNOME:Apps.repo
zypper refresh
zypper install gtk2-engine-equinox
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/GNOME:Apps/openSUSE_Factory/GNOME:Apps.repo
zypper refresh
zypper install gtk2-engine-equinox
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/GNOME:Apps/16.0/GNOME:Apps.repo
zypper refresh
zypper install gtk2-engine-equinox
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/GNOME:Apps/15.6/GNOME:Apps.repo
zypper refresh
zypper install gtk2-engine-equinox