Strange behavior when using CubeRenderTarget Texture as a material's color map

I’m attempting to use a cubeRenderTarget’s texture as a color map for an object’s material and having strange issues. When run locally, I’m seeing the following error, despite that I’m only using the texture in one place: WebGL: INVALID_OPERATION: bindTexture: textures can not be used with multiple targets.

So I tried to recreate a minimal version codeSandbox and I’m no longer seeing errors in the console… but I’m also not seeing the desired effect:

When I use both the envMap material and the map material, I see this:

And when I only create the map material, I see this:

I am realizing that cube textures are not meant to be used as equirectangular images. Is there a way to map a cube texture to an equirectangular image? I see this library for exporting, but am not sure if it has been updated for the latest threejs versions.