Installed libssh.so.4.8.6 according instructions on Ubuntu resulting in /usr/local/lib/libssh.so.4.8.6.
After succesful make install "qjournalctl" gives:
./qjournalctl: /usr/lib/x86_64-linux-gnu/libssh.so.4: no version information available (required by ./qjournalctl)
./qjournalctl: relocation error: ./qjournalctl: symbol ssh_session_is_known_server version LIBSSH_4_5_0 not defined in file libssh.so.4 with link time reference
It turns out qjournalctl uses systems /usr/lib/x86_64-linux-gnu/libssh.so.4.5.0 not /usr/local/lib/libssh.so.4.8.6.