Anyone who has done animation with Gimp knows how useful the animation player is.
I had noticed that animation player was filtering-out the backgrounds on transparent layers.

This is how the layer appeared in Gimp 2.8.22

How animation player showed the same layer.

Animation player reduces all pixels below 30% to transparent.
I wanted to use this effect on all layers but Animation player does not apply it to layers.
I asked a question about it on another Gimp forum and as a result rich2005 wrote a python plugin with a variable slider that works perfectly.
It's called 'clear_alpha.py' and it appears under the 'Layer' menu. The plugin extracts the foreground from transparent layers.
I've found that 26 or 27% works well.