A couple months ago Apple released some code for porting games that supposedly handles having to write custom code specifically for Metal. It's based on Wine so it seems similar to Proton, but Apple probably wants developers to package their games and get them approved for sale on the app store or whatever instead of having users just running their own games. It looked hastily put together when I checked it out, but I don't develop for Macs anymore so I haven't actually used it. It's too soon to tell if game companies care to port their games and go through retesting that the graphics work using the API translation layers to run on different drivers and hardware.