For openSUSE Leap 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/systemsmanagement:Uyuni:Master:Other/openSUSE_Leap_15.6/systemsmanagement:Uyuni:Master:Other.repo
zypper refresh
zypper install dom4j-manual
For openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/systemsmanagement:Uyuni:Master:Other/openSUSE_Leap_15.5/systemsmanagement:Uyuni:Master:Other.repo
zypper refresh
zypper install dom4j-manual
For openSUSE Leap 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/systemsmanagement:Uyuni:Master:Other/openSUSE_Leap_15.4/systemsmanagement:Uyuni:Master:Other.repo
zypper refresh
zypper install dom4j-manual