virtualbox-guest-tools from openSUSE:Leap:15.5:Update 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:Leap:15.5:Update/standard/openSUSE:Leap:15.5:Update.repo zypper refresh zypper install virtualbox-guest-tools