I agree with you. On Solaris I should not have to set LD_LIBRARY_PATH. The location of the *.so files is baked in. The strange part is that postgres starts up without errors and can be accessed from pgAdmin 4. The problem is occurring from the replication functionality. I am beginning to suspect there is a problem with the binary that I downloaded from the postgres site. When I execute ldd -r /usr/postgres/9.6-pgdg/lib/libpqwalreceiver.so there are many symbols not found. I do not know what to make of it just yet. I did reinstall.