you could use the custom stencil “hack”. 4.x reference. https://www.youtube.com/watch?v=PiQ_JLJKi0M
stencil value 1 is green screen. value 2 is foreground elements. it works with 0 writes for foreground elements, but you have a lil more control if you mask them too.
unlit whatever material to block in the stencil value for the green.
and the exposure neutral pp material to puzzle it together
notes: you gotta enable the stencil pass in the project settings and use the default stencil write mode so the depth culling works.
and yes… you have to force the foreground elements into the stencil or the green screen blocker will overwrite everything with it’s value and you can’t go back to 0.