Object Highlighting for Player 1, Not Player 2

I have been looking into methods for object highlighting (outline and full mesh highlighting) with post-process volumes and materials, but I don’t think these methods would work if I have two camera views, and need objects highlighted in only one of those views, such as when dealing with multiple players. I am wondering if there is a method of object highlighting similar to a player camera filter, so that the environment and objects are not being changed? This way, only one player has to see object highlighting.

Or, is it possible to enable a pixel shader for just one player view/viewport window? Not finding any leads on this …