For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tlusk:vpn/openSUSE_Tumbleweed/home:tlusk:vpn.repo
zypper refresh
zypper install openconnect
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tlusk:vpn/15.6/home:tlusk:vpn.repo
zypper refresh
zypper install openconnect
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tlusk:vpn/15.5/home:tlusk:vpn.repo
zypper refresh
zypper install openconnect