Chum needs an older version of libyaml-cpp but symlinking works:
In Terminal as root:
cd /usr/lib64
ln -s libyaml-cpp.so.0.8 libyaml-cpp.so.0.6
(in 32-bit cd /usr/lib)
Then install sailfishos-chum-gui - download from SailfishOS:Chum GUI application — SailfishOS:Chum, a Sailfish OS software repository by the community - with zypper and choose ignore dependencies. Then in Chum set version to 5.0 until told otherwise.