Steinberg UR28 digital output with AES/EBU?

Not exactly a “pass-through” but rather as an auxiliary pair of ins and outs, the outs of which are purposely not processed by the main monitoring circuitry as are the analog outs. They’re typically intended for external signal processing such as effects or recordering.
So yes , not ideal for your intended application. You might on the other hand try adding an A/D converter.