gnome-session-default-session from SUSE:SLE-15-SP4:Update project
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Add repository and install manually
For pool run the following as root:
zypper addrepo https://download.opensuse.org/repositories/SUSE:SLE-15-SP4:Update/pool/SUSE:SLE-15-SP4:Update.repo zypper refresh zypper install gnome-session-default-session