How to detect AC or DC voltage from 9V DC to 250V AC?
Why don't you build a constant current sink that is set up at say 1 mA?
This circuit would be easy to design with discrete components. Worst case power dissipation is managed easily with SMD SOT223 packages.
When the proposed current sink is connected to the DC output terminals of a bridge rectifier AC or DC voltages can be detected.
The simple current sink can drive an LED and the input of a standard optocoupler like a 4N26 for an isolated digital output. 9VDC could easily be detected.