1. Press the following keys in order, one at a time:
F9 Activates the top menu.
o Selects the Option menu.
c Opens the configuration dialog.
i Toggles the use internal edit option.
s Saves your preferences.
2. Working on Debian
Run MC as usual. On the command line right above the bottom row of menu selections typeselect-editor. This should open a menu with a list of all of your installed editors. This is working for me on all my current Linux machines.
3. Open a Terminal and type this command:
sudo update-alternatives --config editor
You will get an list of the installed Editors in your Ubuntu, and you can chose your favorite.