The problem with the above is that an operator will immediately try and put a top-level "address" property, rather than adding that inside the "rpcSettings" block, resulting in: "Unknown configuration keys: [address]." (which is correct in general, but maddening in this case).
From a brief look, it looks like recent changes to RpcSettings turning "address" and "adminAddress" from optional to mandatory triggered the error.
The solution should add the path of the property to the error message.
java.lang.IllegalArgumentException: Can't provide top-level rpcAddress and rpcSettings.address (they control the same property)