For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Vogtinator:boo1174498/openSUSE_Leap_15.2/home:Vogtinator:boo1174498.repo
zypper refresh
zypper install kwin5
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Vogtinator:boo1174498/openSUSE_Leap_15.1/home:Vogtinator:boo1174498.repo
zypper refresh
zypper install kwin5
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Vogtinator:boo1174498/openSUSE_Factory/home:Vogtinator:boo1174498.repo
zypper refresh
zypper install kwin5