Bug Issues reading from depth texture in WebGL - not enabled?

First the setup - working in editor, desktop builds - but not webgl builds. Unity 2021.2.6f1

Code (CSharp):

1. deferredBuffer = new RenderTexture(bufferWidth, bufferHeight, 0, RenderTextureFormat.Default);
2. deferredBufferDepth = new RenderTexture(bufferWidth, bufferHeight, 24, RenderTextureFormat.Depth);
3. deferredPass.mainTexture = deferredBuffer;
4. deferredPass.SetTexture("_Depth",deferredBufferDepth);
5. camera.SetTargetBuffers(deferredBuffer.colorBuffer, deferredBufferDepth.depthBuffer);

And I'm sampling it in a full screen quad (RawImage attached to a UICanvas).
return tex2D(_Depth, i.uv).r;

In builds I see only a pure white screen. Is there some config to enable depth textures in WebGL?

 

User-error. 2D Camera wasn't being cleared, causing render issues in the build.