This version of Unity is unsupported.
Metal
Metal requirements and compatibility

Introduction to Metal

Metal is the standard graphics API for Apple platforms. It’s optimized for Apple devices and thus provides a low-overhead API for the platforms it supports.

Unity uses Metal graphics for Apple platforms by default so there is no need to perform steps to enable it.

Important: Apple deprecated support for OpenGL and OpenGL ES, and you can’t submit applications that use OpenGL/OpenGL ES to the App Store. You should only use Metal to support Unity applications that run on Apple platforms.

Additional resources

Metal
Metal requirements and compatibility