From Blender 2.91, there is now a "compound parent" shape option dedicated to this kind of shape (with concavities):

You can find its description from the release page here.

And in the documentation:

Compound Parent

Takes the collision shapes from the object’s children and combines them.

This makes it possible to create concave shapes from primitive shapes.

This usually results in a faster simulation than the Mesh collision shape while also being generally more stable.

The file below is the demo from David Vogel (all credits to him):

From Blender 2.91, there is now a "compound parent" shape option dedicated to this kind of shape (with concavities):

You can find its description from the release page here.

And in the documentation:

Compound Parent

Takes the collision shapes from the object’s children and combines them.

This makes it possible to create concave shapes from primitive shapes.

This usually results in a faster simulation than the Mesh collision shape while also being generally more stable.

The file below is the demo from David Vogel (all credits to him):