For Kernel stable run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Sauerland/Kernel_stable/home:Sauerland.repo
zypper refresh
zypper install r8168
For Kernel HEAD run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Sauerland/Kernel_HEAD/home:Sauerland.repo
zypper refresh
zypper install r8168
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Sauerland/15.6/home:Sauerland.repo
zypper refresh
zypper install r8168
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Sauerland/15.4/home:Sauerland.repo
zypper refresh
zypper install r8168