For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:im:signal/openSUSE_Tumbleweed/network:im:signal.repo
zypper refresh
zypper install signal-desktop
For openSUSE Factory RISCV run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:im:signal/openSUSE_Factory_RISCV/network:im:signal.repo
zypper refresh
zypper install signal-desktop
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:im:signal/15.6/network:im:signal.repo
zypper refresh
zypper install signal-desktop
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/network:im:signal/15.5/network:im:signal.repo
zypper refresh
zypper install signal-desktop