Question Alpha on renderTextures renders black on Android

I'm taking imposter render textures of scene objects after post processing. These render textures has solid background color because they're captured after post processing. To get rid of solid color background I use a chromakey shader in my render pass. It works well in Editor, but on Android all transparent regions of my render textures turns solid black. I'd happy to not use chromakey shader, but I don't know how to get rid of the solid color background after post processing...

Render texture params:
- depth 24
- format RenderTextureFormat.ARGB32

In editor, and on Android: