For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:alarrosa:packages/openSUSE_Tumbleweed/home:alarrosa:packages.repo
zypper refresh
zypper install sonarr
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:alarrosa:packages/openSUSE_Factory/home:alarrosa:packages.repo
zypper refresh
zypper install sonarr
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:alarrosa:packages/15.4/home:alarrosa:packages.repo
zypper refresh
zypper install sonarr