Yes. It is possible to use TigerVNC without relying on SSH. However, it is important to note that the default connection method in TigerVNC is less secure.
Knowing that, one workaround that you can do is to create a local OpenSSL certificate. This allows you to still use an encrypted channel for your VNC links. Once you have your X509 certificate, you can run: vncviewer ramces@192.168.68.155 -X509CA /path/to/cert.pem to connect to your VNC server.