itch.io

I couldnt find a fix for this either, apparently blender changed the way it handles transparency on materials and you need a 3rd party plugin. when you put them into Unity it looks as you'd expect though

This is 2 years late, but for Blender 3.5.1 the fix is to set the Alpha value on the "alpha" material to 0. For whatever reason its the only material not using a "Principled BSDF" surface so you just need to click "use node" and then set the Alpha to 0.