I have an EOS RP.
I have the Control Ring adapter connected to the camera, and an EF to M42 adapter connected to that. I have set the control ring to control ISO. I have also enabled "Release shutter without lens"... yet the control ring still doesnt work.
It works with all my EF glass, just fine.
My issue here really is more of a complaint I guess. Why is there a requirement for lens communication when using a feature which is entirely independent of the lens and why does it not work even with lens-free shutter release enabled. Completely bricks an amazing piece of tech.
Because the adapter is designed to work all Canon EF lenses. It is not a bug. Find a work around and move on.