/usr/lib/x86_64-linux-gnu/libqgsttools_p.so.1.0 is in libqgsttools-p1 5.5.1-4ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libqgsttools_p.so.1.0.0
/usr/lib/x86_64-linux-gnu/libqgsttools_p.so.1.0.0