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