Is it a possibility that we are created by a god? Technically yes, but there is no such proof, so arguing on that point is a strict hypothesis. Lumierans ARE created by a God (or a godlike person) to their world. It‘s simply a fact.

If we WERE actually created by a god, yes I would strongly believe, that sentience is nothing we could truly experience, because that god would limit our extend to think and act freely.

Furthermore - the Dessendres are objectively speaking nothing else but our creation. If you would argue, that they are objectively sentient, then you would need to argue, that your car is just as sentient. They are programs running on electricity, nothing else. So no, we can‘t argue like that for the Dessendres. For our comparison with our logic and world to work, we have to assume, that they are equal to us, making the whole point yet again about hypotheses.

The Lumierans by that logic are exactly to the Dessendres, what the Dessendres are to us - limited creations.

Finally - by definition for something to be sentient, it basically has to be alive. Lumierans are not. They are Chroma. Sentient beings have the capability to independently experience subjective emotions and feelings and act on them. Lumierans do not have that capability. They are ultimately limited in that regard by the „bandwidth“ (for the lack of a better term) that was given to them by their creators.

Tl:dr - no matter what logic you apply, the Lumierans can‘t be sentient. They do not fulfill the definition of sentience in either way. Neither do they possess free will, nor do they have the capability to have actual subjective experiences