4.4.0-72.93) is not available, but a newer one is (4.4.0-142.168). We redirected you there.
/usr/lib/x86_64-linux-gnu/libupnp.so.6 is in libupnp6 1:1.6.19+git20160116-1.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libupnp.so.6.3.3