After some fiddling I finally got OpenCL working on my new MacBook Air with the M1. Basically it was only a matter of finding the right settings with some trial and error, the current blender code is already up to the task.
I did not test very much yet, but the famous BMW renders in about 3:40 minutes (GPU and CPU combined).
As I totally understand the reasons behind the deactivation of OpenCL on macOS in blender, my question is:
Is it possible to add some small additions to the deactivated macOS-parts or even turn it on for the M1 by default as long as there is no official support yet? Maybe it is useful for other users too.