Connect to VNC server

Locally from macOS based client

• Either type open vnc://[host_name]:[port] in Terminal or vnc://[host_name]:[port] in Safari or other browser
• You can omit :[port] if your server is using a default port (5900)
• A default Screen Sharing app will open and you can type-in VNC username and password

Over SSH tunnel from macOS based client

• Create SSH tunnel to the server: ssh -L 5900:localhost:5900 [alias] (see more about SSH here)
• This will forward everything from the local port 5900 to the remote port 5900 via SSH tunnel
• Open VNC client: open vnc://localhost in Terminal or vnc://localhost in Safari
• You can create an alias in your ~/.zshrc in order to connect just by vnc:

alias vnc='/usr/bin/open -a Safari vnc://localhost && ssh -L 5900:localhost:5900 [alias]'

Setup VNC server

macOS

• System Preferences -> Sharing -> Screen Sharing

Ubuntu

• Settings -> Sharing -> Remote Desktop
• Enable Legacy VNC Protocol and in three-dot submenu select "require password" (needed for connections from macOS's Screen Sharing app)
• It's not possible to connect when there are no active user sessions (after restart), as a workaround you can enable Automatic Login in Settings -> Users. However, Automatic Login doesn't unlock GNOME Keyring, so VNC will not be able to accept connections, as a workaround you can set empty password for login Keyring in Passwords and Keys. More information: How to Enable Remote Desktop in Ubuntu 22.04
• Additionally, if there is no monitor plugged-in, you have to add fake display - more info
• You may also encounter issues with clients not able to connect via SSH tunnel randomly. In that case verify the connection on the client via netstat -an | grep 5900, if you see FIN_WAIT or CLOSE_WAIT in there, it means that your connection isn't properly established. You can try adding ServerAliveInterval 60 and ServerAliveCountMax 30 to the specific host in your ~/.ssh/config.