How to configure ADC input (ADS8681) for AC mains measurements
It sounds like this should work: -


But this will also make a big low pass filter to the input right?

No, not as far as I can tell. After all, for a LPF you need a capacitor and I see nothing that is going to be significant given the effective source impedance into the inputs of circa 10 kΩ. You might choose to add a capacitor across the 10 k in the voltage divider for anti-alias prevention of course.


I'm not clear how to properly configure (hardware and software) the
ASD8681 for high voltage AC measurements.

Not sure what you need to do here because it's unclear what you don't know.