Install libopenthreads20 by entering the following commands in the terminal:
sudo apt update sudo apt install libopenthreads20
Object-Oriented (OO) thread interface for C++, shared libs
This library is intended to provide a minimal & complete Object-Oriented (OO) thread interface for C++ programmers, used primarily in OpenSceneGraph. It is loosely modeled on the Java thread API, and the POSIX Threads standards. . This package contains the shared libraries.