What's the best way to render out an alpha channel in an eevee animation

I gather this is one of those ‘don’t we all wish that was in Blender’ issues? But basically I want to either include an alpha channel in my rendered EXR animation sequence, or if need be, render out a black and white sequence separately. Only thing is, while I can create a pure black and white via the viewport shading options…

When I try to render the animation, it goes back to full eevee mode and looks like the final render. I can choose workbench in the render engine type, but the color/shading options there are limited and it just looks like light grey over dark grey instead of white over black.


man, this used to be a place where you could get answers. So sad.