Is it ok to use an enamelled Dutch oven on an electric stove top with the older ring burners?
Oh sure, you can use an enameled Dutch oven on that type of stove. That type of burner (hob) is still the most common in the US; I haven't had anything but that type (in my home) in my adult life. An enameled cast iron Dutch oven will discolor when used on any stove, but it wont crack unless allowed to burn "dry" or if the pan was defective to begin with.