I don’t understand Background in the new beta. No matter what I do - I get black. I choose Color instead of Sky, I get black. I turn off that channel and only use the color slot next to Background - I get black.
I think I’ve tried every combination of turning one slot off and the other on and vice versa and both on and both off, and I still get black.
At VfR2 there was the same behavoir. You need to disable the alpha output channel. But at the VfR3 this option is not available yet. Reported, but not confirmed as bug, could be a feature.
At VfR2 is use the alpha output always. But if I need the background, than the image browser XnView allow me to easy switch on/off the transparency of PNG. So, I was able to see the background. Maybe it works for VfR3 beta so too.