gtk2-metatheme-equinox from openSUSE:Backports:SLE-15-SP1 project
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Add repository and install manually
For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/openSUSE:Backports:SLE-15-SP1/standard/openSUSE:Backports:SLE-15-SP1.repo zypper refresh zypper install gtk2-metatheme-equinox