Rendering background help (3D)

I’m having an issue with rendering my background on a 3d project.
I have a Canvas for the UI with it’s camera, as usual. I have a main camera for the main gameplay part and an extra Canvas with just the background.

The idea is to render the background first, then the gameplay, then the UI above it. However, it doesn’t matter what i do, the gameplay camera covers the background with a solid black color (I tested every clear flags available on the camera) instead of just leaving the already existent background.

I know that if I change the Render Pipeline in the graphics settings to the legacy builtin-forward pipeline, everything renders correctly, but I lose a outline effect i have and need.

What do I need to do to be able to render the background behind the gameplay? Any settings I need to change?

To sum it up:
3 cameras - 1 for BG, 1 for Gameplay, 1 for UI.
Their priorities are set correctly (BG renders first, then gameplay then UI)
But the gameplay camera removes what was rendered by the BG camera. IDK what to do

Pls have a try RenderTexture. here is the link for you. https://docs.cocos.com/creator/3.8/manual/en/asset/render-texture.html


Have you tried this?