Para 16.0 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:andreas.osterburg:Radicale/16.0/home:andreas.osterburg:Radicale.repo
zypper refresh
zypper install Radicale
Para 15.6 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:andreas.osterburg:Radicale/15.6/home:andreas.osterburg:Radicale.repo
zypper refresh
zypper install Radicale
Para 15.5 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:andreas.osterburg:Radicale/15.5/home:andreas.osterburg:Radicale.repo
zypper refresh
zypper install Radicale