/usr/lib/x86_64-linux-gnu/libOpenThreads.so.20 is in libopenthreads20 3.2.1-7ubuntu4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libOpenThreads.so.3.2.1
/usr/lib/x86_64-linux-gnu/libOpenThreads.so.3.2.1