There's no "one size fits all" approach to scene managers. The simple reason is that every game is different, with a different interpretation of what a scene involves, which resources it provides, how many there are, and whether they're hardcoded into the application or loaded from an external file. Especially in the latter case, there's a major concern with respect to what the (serialized) scene format looks like.
Describing what a scene should look like can be very simple, with the easiest format being just a description in text format of what the position of each object in the scene is, and the more advanced formats defining specific parameters of each object, from specific shaders and textures to the game logic.
Most of the tutorials that you'll encounter online and elsewhere regarding scene managers will usually cover this basic type. These often involve hardcoded logic for switching between particular scenes and calling a particular function for each scene to construct...