For openSUSE Leap 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:vpn/openSUSE_Leap_15.6/network:vpn.repo
zypper refresh
zypper install strongswan-ipsec
For openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:vpn/openSUSE_Leap_15.5/network:vpn.repo
zypper refresh
zypper install strongswan-ipsec
For openSUSE Leap 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:vpn/openSUSE_Leap_15.4/network:vpn.repo
zypper refresh
zypper install strongswan-ipsec
For SLE 15 SP5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:vpn/SLE_15_SP5/network:vpn.repo
zypper refresh
zypper install strongswan-ipsec
For SLE 15 SP4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:vpn/SLE_15_SP4/network:vpn.repo
zypper refresh
zypper install strongswan-ipsec