1)Lambda syntax error due to recent change in tuple unpacking syntax in python 3. 2)PyInstaller does not love Packages poorly designed by using sys to change paths or we can say the "Hidden Imports". So basically the whole point of using mapview in kivy was to make a application and if Pyinstaller does not recognise it, Then you are in trouble.
So this is basically a workaround idea which worked very well for me. So basically I croped out all the code line by line from different folders of their original package and make it into a single .py file which >>you can download and just use it by copy pasting in your main python file on top of all your code.
Here's an example of making an app and placing a marker.
class MainApp(App):
def build(self):
self.title = "Your_app"
object = MapView(zoom=4, lat=26, lon=75)
m = MapMarker(lat=26, lon=75)
object.add_marker(m)
return object
if __name__ == "__main__":
MainApp().run()