Description
Due to a problem in the Quartus® Prime Software version 15.1 for Linux, you may see this missing library error when you open the Stand-Alone Programmer.
Resolution
To work around this problem, create the symbolic link libprotobuf.so -> libprotobuf.so.8.0.0 in quartus/linux64 directory with the following command:
ln -s libprotobuf.so libprotobuf.so.8.0.0
This problem is scheduled to be fixed in a future version of the Quartus Prime software.