As far as I understand https://eips.ethereum.org/EIPS/eip-831 EIP-681 should be backward compatible with ERC-67. Assuming the last state of ethereum/EIPs#67 then it is possible to add raw hex data for a transaction via the data param. This is not supported by the EIP-681 implementation of kethereum (everything is put into function params). I tried generating a ERC-67 uri with data and use it with Walleth, which did not work (the data is dropped)

Note: it might be that this should be discussed on some EIP thread, but I couldn't find a good one.