Ubuntu GNOME remix uses the GNOME3 shell. This will override the button layout from the windows manager preferences.
To have all windows buttons on the left side as it is in Ubuntu/Unity we can run:
gsettings set org.gnome.shell.overrides button-layout "close,minimize,maximize:"
or any other button layout. Also see this question:
From the GUI we can run dconf-editor, browse to the key org.gnome.shell.overrides to replace the entry
:close with our custom key
close,minimize,maximize: for the traditional button layout:
Note: as soon as we change the button layout from the GNOME Tweak tool it will be moved back to the right side.