Not all the codes on these cars are the same. But yes most are.
As far as I know no one is using the OVMS app on the I oniq.
Unless you are willing and able to do some development work to fix any problems, I would not recommend OVMS for the current I oniq.
Why would you recommend against using it? And what do you think won't work? As I understand it the worst that can happen is the CANbus receives a command it doesn't like or understand and just ignores it....?
I've looked at EVNotify but it doesn't do much compared to OVMS, and from what I've read since it's mostly simple OBD vs CANbus based once the OBD side of things goes to sleep after the car has been turned off, it disconnects and becomes useless. I'll look at it some more, but aside from seeing SOC via Bluetooth (another limiting factor) it's very limited compared to the connectivity and features of OVMS.