Getting the scene an object is in (blender 2.9) It's fairly easy to get the objects that are in a scene:
dict(myScene.collection.all_objects) # mapping from name to object.

But how to go the other way?
scene = magic_get_linked_scenes(myOb)

One could iterate through all scenes:
linked_scenes = []
for scene_name, scene in dict(bpy.data.scenes):
  for ob_name, ob in dict(scene.collection.all_objects):
     if ob.name == name:
         linked_scenes.append(scene) # checking object equality should also work. 

But this is clumsy and slow if there are a very large number of objects. Is there a better way?
object.users_scene seems to show the scenes using the object.
Blender's Python Console is very useful when finding this stuff out. If you start typing and hit Tab Auto Complete shows you all the options you have: