I had a friend who wanted me to help him set up a wireless router. Unfortunately, it was difficult for me to guide him over the phone, and he came up with a great idea that I could take control of his screen using teamviewer. He uses Windows.
The next step was to know if teamviewer was cross-platform and could be run on Linux. Fortunately, teamviewer had packages for the main Linux distributions like Fedora or Ubuntu.
Once installed, I could share his screen and configure his wireless router. If you need a cross-platform free software to control other desktops remotely, you can use teamviewer. It is very convenient for non-commercial use and works across multiple operating systems.
Teamviewer actually uses wine on Linux to run.