To reproduce:
1. Open attached project;
2. Open "Main" scene;
3. In the Game view you will see a cube in a background of blue dots;
4. Go to player settings;
5. Switch Graphics API to DirectX11;
6. In the Game view you will see a cube in a white background.

Expected result: The background of render texture is with blue dots.
Actual result: The background of render texture is white on Directx11.

Reproduced on versions: 5.6.0b1, 5.6.0b5;
Not reproduced on versions: 5.4.4p1, 5.5.0p4.