For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:libs/openSUSE_Tumbleweed/multimedia:libs.repo
zypper refresh
zypper install fdk-aac-free
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:libs/openSUSE_Slowroll/multimedia:libs.repo
zypper refresh
zypper install fdk-aac-free
For openSUSE Factory PowerPC run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:libs/openSUSE_Factory_PowerPC/multimedia:libs.repo
zypper refresh
zypper install fdk-aac-free
For openSUSE Factory ARM run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:libs/openSUSE_Factory_ARM/multimedia:libs.repo
zypper refresh
zypper install fdk-aac-free
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:libs/15.6/multimedia:libs.repo
zypper refresh
zypper install fdk-aac-free
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:libs/15.5/multimedia:libs.repo
zypper refresh
zypper install fdk-aac-free