How do I activate the webGPU in a complex scene?

This error:

logger.ts:103 BJS - [16:40:37]: WebGPU uncaptured error (1): [object GPUValidationError] - 
[Texture “Texture2D_opaqueSceneTexture_1024x1024x1_wmips_rgba16float_samples1”] 
usage (TextureUsage::(TextureBinding|RenderAttachment)) includes writable usage 
and another usage in the same synchronization scope.

means that you are indeed using WebGPU. However, this error should not occur: are you able to share a link to your project so that we can have a deeper look?

Unfortunately, you won’t see any significant difference just by switching to WebGPU. What you could try is enabling the snapshot rendering mode: