Originally Posted by 1989Pre

The crank arm is far too close to the outer chainring to fit a cage in between. Ebay member Velomadison informs us in his current offering description that:

"These are not designed for a front derailleur, rather to be set up with
one or the other for different desired gearing, often with a rear wheel
with butterfly nuts."

There is 1-2mm of space betwen the crank arm and the rivet(s)..