Webgpu and THREE.ShadowMaterial

How to get the same result as the ShadowMaterial with the webgl2 renderer but for webgpu renderer ?

i use it for an transparent ground object:

this.ground = new THREE.Mesh(new THREE.PlaneGeometry(200, 200), new THREE.ShadowMaterial({color: 0x000000, opacity: 0.6}));

Obviously this work fine with webgl2 and here is the error i get when using the ShadowMaterial with webgpu.

I just see there is a new r164 and this revision fix it.
note: i was using the r163.

Sorry for the question for nothing.