Cannot access Zorin PC using x11vnc from MacOS

Trying to access newly installed Zorin PC (Zorin-OS-17.1-Core-64-bit-r1.iso) from MacOS Sonoma using RealVNC Viewer app on Mac. I installed x11vnc on Zorin without apparent issues and the command 'ps -eaf' shows x11vnc running. RealVNC Viewer connect operation fails almost immediately with error 'The connection closed unexpectedly'. This occurs even if the firewall (ufw) on Zorin is disabled. Any ideas how to get this working?