I'm using GLES2.
I was using 3.1.1 and I did't have any shadow on Android: https://godotengine.org/qa/43524/2d-shadow-not-showing-in-android .
I updated to 3.2.1 and I now have shadows on Android too (I didn't have the problem on Linux and web (even from android) before either).
But the detail is low and it looks like a saw (only if it's further away):
The wall is a tilemap with light occlusion.
How can I change the fineness so that it looks smoother and aligned with the wall?