For openSUSE Leap 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:misc/openSUSE_Leap_15.6/devel:languages:misc.repo
zypper refresh
zypper install ffcall
For openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:misc/openSUSE_Leap_15.5/devel:languages:misc.repo
zypper refresh
zypper install ffcall
For openSUSE Leap 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:misc/openSUSE_Leap_15.4/devel:languages:misc.repo
zypper refresh
zypper install ffcall
For SLE 15 SP4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:misc/SLE_15_SP4/devel:languages:misc.repo
zypper refresh
zypper install ffcall
For SLE 15 SP1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:misc/SLE_15_SP1/devel:languages:misc.repo
zypper refresh
zypper install ffcall
For SLE 12 SP5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:languages:misc/SLE_12_SP5/devel:languages:misc.repo
zypper refresh
zypper install ffcall