The big problem with clip on electronic tuners and an autoharp is finding somewhere to clip it.
You can clip to a tuning pin, but they are small and it can be awkward to keep it in place.
Most tuners are designed to clip onto the headstock of a guitar and will not open wide enough to clip to the body of an autoharp.
We found that the Intelli tuner has a clip which opens just wide enough to grip the full thickness of an autoharp.
Quack!
GtD.