I'm using the Mixamo Control Rig with a rig very similar to the Mixamo one, the difference are a few extra joints, please see the selected joints in the screenshot.
Everything works fine with the rig, just those joints are left behind. I thought of including the extra joints in the bind hierarchy as seen in the screenshot below.
This works, but the forearms behave strangely.
I wonder if there is a better way to make this rig work with the Mixamo control rig.