Ok my batteries are 160V so probably helps with a detectable level of current for my CTs. What sort of DC current flows there in your system? Would a CT detect it? You can wind the cable around them multiple times to upscale it, assuming the cable will bend enough!
After that you are into intrusive options like shunt resistors and current sensor boards but you will have to decide how safe those are, insurance risk etc.

Software interfacing would be a great option as it is so customisable compared to hardware solutions. These always have a valid range of operation which means many options are not suitable.

The other thing I looked at was the main chip inside the Harvi can read all sorts of protocols including i2c which is what the Arduino can output! But it would require significant changes to the Harvi and probably more knowledge than I have. But it would cut out all the AC current creation and just tell the Harvi the current level directly, but still would need the CT clamp to detect it.

Also try posting on the myenergi forum and I think there was a Home Assistant forum too?