For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network/openSUSE_Tumbleweed/network.repo
zypper refresh
zypper install otter-browser
For openSUSE Factory ARM run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network/openSUSE_Factory_ARM/network.repo
zypper refresh
zypper install otter-browser
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network/15.6/network.repo
zypper refresh
zypper install otter-browser
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network/15.5/network.repo
zypper refresh
zypper install otter-browser