Just for everyone who is scared by this statement - macOS on Apple Silicon still supports OpenGL and OpenCL, but it is emulated on top of Metal now.
You might want to look at: https://www.phoronix.com/scan.php?page=news_item&px=Zink-mac... though. Maybe there'll be more interest for a direct OpenGL to Metal layer not built by Apple in the future, for having a newer feature set.
Just for everyone who is scared by this statement - macOS on Apple Silicon still supports OpenGL and OpenCL, but it is emulated on top of Metal now.