LWRP: Multiple layers of blurred UI possible?

I know that GrabPass no longer works, and a camera texture is available after opaque/alphatest/skybox. However for UI I also need transparent objects to be included, such as water. I have managed to do this using a ScriptableRenderFeature/ScriptableRenderPass.

The issue is that I need to render a UI canvas, and then blur the result to be used for a second canvas. I thought I could use multiple cameras and do the Screen Grab after the "RenderPassEvent.AfterRendering." However multiple cameras are not supported in LWRP.

Is it possible to achieve what I want in LWRP, or am I stuck with the built in render pipeline?

An example is below.