Very nice! I am struggling to achieve a similar result with 3DTilesRenderer however unsuccessful so far.
Are you willing to share the setting you used for the DirectionalLight and shadow.camera ?
I guesstimate a lot of values so, you can always ask me if some stuff doesn’t make sense.
If I had to do it again, I would use the cascade shadow map sample. Especially if you’re not rendering the entire google earth dataset but still a large area, I think that’s the way to go.