Within the Spotlight field, enter vnc://your_server_ip:5900 (e.g.Access the 'Spotlight' by hitting CMD + Space-bar.Turn on 'Screen Sharing'- select 'Allow connections to control the screen' and 'Require a password' underneath 'Access Options' then proceed with the below instructions to remotely access your Ubuntu 18.04.2 LTS desktop from your macOS desktop.Within 'Settings', scroll down to the 'Sharing' tab within the left-hand side of the window.

Evidently, vino functionality was merged in Ubuntu 18.04.2 LTS Gnome Control Center, so it's much easier- simply go to 'Settings'.After noting the local-IP address of the device, proceed with the next set of instructions from your macOS desktop. Retrieve and the device-IP address by running ifconfig -a the local-IP address of the device will be returned within the terminal-output under the field: 'inet addr:' (e.g.Run sudo-reboot and then log-in to the Ubuntu 16.04 desktop.After the vino application preferences window prompts, ensure that the 'Allow other users to view your desktop' and 'Allow other users to control your desktop' options are selected beneath the 'Sharing' field it is also recommended to select the 'You must confirm each access to the this machine' and 'Require the user to enter system-password'.

Download and install vino by running sudo apt-get install vino within the Ubuntu terminal.

I successfully logged-in remotely from my iMac macOS Mojave desktop into my hackintosh, which is a retrofitted 2012 Apple Macbook Pro running smoothly Ubuntu 16.04:

Apple remote desktop linux client